Can I still ask her out if she has a date?

Leave it. She's interested enough in this guy to have accepted an invitation to go out with him. Even if it doesn't work out between them, she didn't turn him down because she'd rather spend time with you.

Feel like my whole world just shattered before me. I was literally just about to ask her out on a date today, and within moments of getting ready to ask she brought up that a guy has invited her out for a meal and was asking me whether I thought it was a date or not. I actually can’t believe my luck. Is it still worth asking her out, or should I just leave it and move on.
Why does the universe just like to **** on me sometimes. Anyone have any similar experiences so I know that I’m not the only one with god awful luck? Is it worth still trying to pursue this?

Leave it. She's interested enough in this guy to have accepted an invitation to go out with him. Even if it doesn't work out between them, she didn't turn him down because she'd rather spend time with you.

Just rock up to her (jacket over shoulder), flash your cheekiest grin, then say, "Why you dating a zero, when you could be with a hero?", , kick the jukebox to play N*Sync- Girlfriend and she'll drop him like a hot potato and be yours in a second. Job done 😎
OK, serious answer now, I think the important lesson to take is that hot / desirable girls are noticed by everyone... and if you like her, you can bet that there are at least 1-2 other guys who've also clocked her. Therefore, it's a better idea to show your interests early on, so you don't give another guy a chance to get in before you (yes, I've had this before, so I know how much it sucks). The other thing is, if you ask her out quickly, then it's not so bad if she says "No" (for whatever reason), as you haven't built it up in your head so much.
Well that's a lesson to take from this... what should you do about this girl now? One date doesn't exactly equate to a marriage proposal. At least wait until they've had their date before trying anything... it may not work out, in which case you can approach her again. On the other hand, if she does seem to like him, then yes, move on (but bear in mind what I said about moving quicker next time).
TBF, did she know that the OP was interested in her? We don't know how excited she was about the date... after all, her saying "yes" can mean anything from "You'll do for now" to "You're the one I want to be with".

Great advice from Ciel and Old Skool Freak about being positive and going for it and not procrastinating.
To which I'd add: don't live with a scarcity mindset, live with an abundance mindset.
You shouldn't feel like your whole world has shattered because of 1 setback with 1 potential girlfriend. You should be aiming to set up an active dating sales funnel. Where you're breaking the ice with lots of women you're attracted to.
There are a lot of wonderful women out there. Don't get fixated on one till one is very much fixated on you.
It also seems that you're taking yourself and your life too seriously. Especially the negative stuff. Lighten up! Take yourself less seriously, especially the bad things and the things that stress and worry you. This is a change you can make overnight. By simply taking a very zoomed out look at your life and deciding that from now on you'll be a lot less serious.
In doing so you will make yourself more attractive to women.

Don't be passive, don't sit on the sidelines. Be proactive. Go for what you want. Preferably in ways that maximise your chances of success.
From her point of view, it will be a nice situation to be in, if she has a choice of 2 guys to go on dates with.
The inner you should be confident that you're a much better man to be her boyfriend than the other chap. With this being something you don't boast about. You just have that inner confidence.

Feel like my whole world just shattered before me. I was literally just about to ask her out on a date today, and within moments of getting ready to ask she brought up that a guy has invited her out for a meal and was asking me whether I thought it was a date or not. I actually can’t believe my luck. Is it still worth asking her out, or should I just leave it and move on.
Why does the universe just like to **** on me sometimes. Anyone have any similar experiences so I know that I’m not the only one with god awful luck? Is it worth still trying to pursue this?

Thanks for this! Yeah, I’ll just watch how things play out for the time being as I don’t want to interfere with anything. It just feels like a massive kick to the balls because we actually had a decent thing going and I expected that she’d say yes if I did ask her out. That’s just life I guess though.
I’m terms of how excited she felt about the date - not very from what I can tell. Found it a bit odd but I suppose it might play more into my favour.

Just rock up to her (jacket over shoulder), flash your cheekiest grin, then say, "Why you dating a zero, when you could be with a hero?", , kick the jukebox to play N*Sync- Girlfriend and she'll drop him like a hot potato and be yours in a second. Job done 😎
OK, serious answer now, I think the important lesson to take is that hot / desirable girls are noticed by everyone... and if you like her, you can bet that there are at least 1-2 other guys who've also clocked her. Therefore, it's a better idea to show your interests early on, so you don't give another guy a chance to get in before you (yes, I've had this before, so I know how much it sucks). The other thing is, if you ask her out quickly, then it's not so bad if she says "No" (for whatever reason), as you haven't built it up in your head so much.
Well that's a lesson to take from this... what should you do about this girl now? One date doesn't exactly equate to a marriage proposal. At least wait until they've had their date before trying anything... it may not work out, in which case you can approach her again. On the other hand, if she does seem to like him, then yes, move on (but bear in mind what I said about moving quicker next time).
TBF, did she know that the OP was interested in her? We don't know how excited she was about the date... after all, her saying "yes" can mean anything from "You'll do for now" to "You're the one I want to be with".

Yes you can, one of the unfortunate (though not in your case) features of modern dating is that many women do date multiple men.
Make sure your date is before his however and make it pretty clear that you won't tolerate her dating other people men if she wants another date (basically, shove the other guy out of the way in her head).
Be prepared for rejection though if she has enough calibre not to be dating multiple people and also be prepared for rejection in the sense that she may already be more invested in the other guy, there's no guarantee you can win.

Thanks for this! Yeah, I’ll just watch how things play out for the time being as I don’t want to interfere with anything. It just feels like a massive kick to the balls because we actually had a decent thing going and I expected that she’d say yes if I did ask her out. That’s just life I guess though.
I’m terms of how excited she felt about the date - not very from what I can tell. Found it a bit odd but I suppose it might play more into my favour.

So why didn't you date her to find out more about her, rather than the other way round? When i first met my now-boyfriend we were dating after 4 days. Plus you know what they say about treatment of service staff revealing someone's character...

The original poster will have more chance of success if he takes a mildly amused stance at the thought of this woman dating someone else. Trying to make it clear to her that he won't tolerate her dating other people would be a recipe for failure.
A George Clooney or a Brad Pitt wouldn't be worried at all about the competition. So why should the original poster?

The original poster will have more chance of success if he takes a mildly amused stance at the thought of this woman dating someone else. Trying to make it clear to her that he won't tolerate her dating other people would be a recipe for failure.
A George Clooney or a Brad Pitt wouldn't be worried at all about the competition. So why should the original poster?

It is what it is.
I think all you can do is play this one by ear, and let her know that you do think she's attractive. I'm not talking about declaring undying love or anything like that... but a couple of compliments about how she looks should plant the seed.
Thinking about it, you'd be better off going through her friends on finding out how excited she is about the date (if you know them well enough); it's bound to have come up in one of her girly chats... to you, she may just be playing it cool?
By the tone of his replies, I think he's learnt his lesson now, and will move quicker and more decisively in future. I think we're all a bit guilty or procrastinating from time to time.
I'll never forget reading about George Clooney getting blown out by a café waitress once, because she agreed to go home with someone else earlier... so if an "A" list Hollywood celebrity can get blown out, then it's proof it can happen to anyone.

This is such beautiful advice - But if I look hideous, how do you suspect I change myself? Focusing on academic life right now, but I just want advice for a headstart