Why is she still avoiding me?

Does this mean that I have creeped her out?

At the end of last year (literally the last weekend of the final year), I told this girl I really liked her and made a move on her, which I now realize was a mistake. It was at about 2 in the morning after a night out clubbing in a big group. We were on the night bus home and I had had a few drinks and did nothing more than put my arm round her. She said she wasn't interested though. I only made a move on her because she had been telling me how she thought I was cute acting flirty with me on and off for months before that. That night out was literally a year ago. I have seen her once since then at a gathering for our uni group at a pub at Christmas, and she pretty much ignored me so I just ignored her back. Anyway I found out there was a get together in London recently, and she refused to go if I was there so I didn't get invited (actually I think this has happened quite a few times). I feel pretty upset tbh. I didn't message her or anything at all after she rejected me, just put it down to experience but she seems to hate me or something. Why would she do that?

I also forgot to say. On the night bus, "in a moment of drunken sincerity" I actually told her that "I really loved her". I think I said it because I had seen it in a film, and it had worked for this guy. Could this be the reason that she is uncomfortable?

The worst thing is, she appears to have excluded me from the uni group, and because she is attractive and popular, people are happy to go along with her. I know they have been out loads recently and I could have used a few nights out as my social life has been pretty thin recently to be honest. But if she didn't want me to make a move, why was she complimenting me and telling me I was "so cute" (her words, and not just once, like several times).

there is something you aren't telling us.

I also forgot to say. On the night bus, "in a moment of drunken sincerity" I actually told her that "I really loved her"

Girls can sometimes get funny when their guy-mates suddenly confess that they have feelings for them. I don't know the full logic, but from their point of view, it's like the whole relationship was built on a lie (not saying I agree with it, just how they see it sometimes).
It's more likely you misinterpreted signals form her, and possibly saw something that wasn't (really) there. Some girls are naturally very tactile (e.g. touchy-feely), and this can often lead to blurred lines. Others like to make people feel good about themselves by saying nice things about them & building up their ego. Can you be absolutely sure all this behaviour was specifically directed at you? It's likely she was like this with a few or several other people as well.
Depending on how drunk she was, she may well have thought you were trying to take advantage of that (I'm not accusing you, just giving you some ideas... after all, we don't know what she may have experienced in the past).
Well unless you're a hormonal teenager, it's a pretty big deal to tell someone that you "really loved her".
Forget pretty much EVERYTHING, you've ever seen in a Rom-Coms... as it's all lies (you have my permission to sue Adam Sandler et al for misrepresentation lol). In those films, yes it's always the nice but goofy guy who gets the hot babe in the end... how often does that happen IRL? Relentless persistence pays off in those films... IRL, it just screams "STALKER".
Anyway, just another small thing I wanted to pick up on:-
I can understand the crowd perhaps choosing her over you (not really nice or fair, but I get it)... but if they were your friends, surely a few of them could have arranged a smaller social without her present (say, 4-5 of you... or even 1-on-1), no? The fact that no one could be asked to even do that over a year suggests either:-
a) They didn't (really) like you and you were just there for convenience or to make up numbers
b) She's poisoned everyone in that group against you.
Either way, I agree with the other posters who said you should just cut your losses and make new friends / social circles. Obviously, take the lessons from this sorry scenario.