Was I Just Used? (Muslim Brothers and Sisters Please Also)

Not Muslim here so feel free to disregard if thats what you want, but if you love her you would wait for her more right? If she honestly is not ready for marriage because she is prioritising education and wants a stable job to be financially ready for marriage / married life then you should trust her and give her the time to be ready. If she has gone cold, perhaps she is stressed over uni at the moment if its the very end of her studies - I was the same at the end of university too. Have a conversation with her and explain that you are ready for it, but try to trust her too. For a woman, completing studies and getting a career is really important when married life has always been seen as the "end" of a woman's independent life as she is suposed to care for the husband alone. Maybe she is worried she will lose that sense of independence in marriage.
The only thing to be worried about in this situation (and again it depends on your level of trust in your partner), but its whether she is questioning if you're the man she does want to marry. If she says she just isnt ready but does not suggest that she doesnt want to marry you specifically, then you should be able to wait for her.

It sounds like you've approached this in quite a transactional way: You provide for her, woo her, make niyyath, make dua in her name, perform umrah, be supportive and IN EXCHANGE your expectation is that she marries you. But in fact it doesn't sound like she ever agreed to that, or asked you to do any of those things. So no, she hasn't used you; you just decided to do those things.
At the end of the day it's her decision whether she marries you or anyone. It's completely reasonable to say she's not ready and she doesn't need to "give anything legitimate behind" that. It's not pleasant but if she's gone dry and unresponsive, I'd take that for your answer and move on.

People are allowed to doubt things .. to change their minds… think of this outside the emotion for a second. You will see her POV

I don’t really get any sense that she used you. This is just the way that most relationships end, one person not being that into it any more and the other person being a bit blindsided and looking for logic behind it.

Sorry but can you clarify your point a little please. Are you saying what she first wanted she’s just had reservations about it hence why she’s said what she said and is being the way she’s being.

She might have changed her mind or have cold feet. It’s not an irrational thing. People can accept one thing and later on, feel quite different about it. Something may have happened that made her feel this way or maybe nothing has happened and she’s just not ready. Either way, at least she’s being direct with you.
You keep asking why won’t she make time for you and that surely you wouldn’t be busy for someone you love, but sometimes people have certain situations that come up and distract them. She may be mentally, emotionally and physically drained and that’s why she’s being blunt. Or perhaps she’s just scared. Give her time. For three years it’s been all talk, yes there have been actions on your part, but has she done anything to act on her part? It’s most likely settling in, what her life would be like with you and being married. People can change how they feel within a matter of moments. She doesn’t need to devote her time to you, she isn’t obligated to. She may need some time alone and it would be better for the both of you if you take some time to reflect on this next step.

So taking into consideration and onboard that her mind or this cold approach is her approach going forward. And acknowledging something may have been influential towards this happening and for her to feel the way she’s feeling as of now. The best thing to do is just give space..What are my next steps if you don’t mind me asking or what should I take into consideration for next steps then since you’ve said it’s time to reflect?

She could be feeling this way for a variety of reasons. I’m Muslim too, so I understand why she might be feeling pressured or perhaps scared. (That is IF she’s feeling this way). It’s uncertain why she’s acting so coldly towards you, and the only way you’ll know is if you ask her. I would give her some space for a little while, not too long, however. Then come back to her if she hasn’t started a conversation with you and ask if you two can talk about your current relationship. Don’t jump right into the interrogation. Start off by asking how she is, and if she’s feeling okay. Ask her why she’s been acting differently if something has changed and remind her that it’s okay to admit the truth and that she shouldn’t feel scared or pressured to do something she doesn’t want to. Then if the conversation is going smoothly (smoothly compared to what your usual deep talks would be like), ask her if she would still like to get married and if she’s having any doubts.
Something has changed from what it seems, you will need to give her some time and wait to see if she comes to you first. If she doesn’t, you may need to remind her that you’re still there for her, but you’re not going to enforce anything on her. This sounds like a lot, but it will most likely seem natural when you do this with her. Your most important step is to figure out what suits HER best, based on who she is as a person. Does she like space? Does she like clinginess? Does she like being independent? It helps when it comes to difficult situations like this.

She's been through a lot of stress now from studying. She needs some time to rest and relax before going through something stressful again (marriage). Marriage is a huge thing for both of you, so the whole preparation thing is very stressful and I think she doesn't want to put everything on you (especially financially) so she would probably want to start a good job first.
She never said anything about not wanting to marry you. You are pressing her and it makes her feel uncomfortable and stressed so she is distancing from you. Doesn't mean she doesn't love you.
Maybe talk with her about it in a way that she will see that you are trying not to put her under pressure. Like ask her what would she want to do after university. Explain that she means a lot for you and you will continue supporting her.
I am not a Muslim.

Sorry but can you clarify your point a little please. Are you saying what she first wanted she’s just had reservations about it hence why she’s said what she said and is being the way she’s being.

You are so young! You will meet many! Not all relationships work out. Trust god and move on

And what if they turn out to be the same.

Space it is. No there’s never force behind anything. Hard to understand what’s changed although something must have influenced her mind. I have been there for her since the very first day so she knows I am there for her nevertheless. I just question was there ever anything wrong being a clingy partner and showing that much love and affection for her and expecting her to reciprocate it back to me if so I guess I’ll just keep to myself really.