she said she made a "huge mistake."
When someone says it was a mistake, usually what they really mean is it was bad timing. Most of the time. Don't take it personally, there's plenty of people out there, but it's usually a "okay I left them, now I am all alone, crap".
Couple months of relatively smooth sailing. Since January, she's been getting more distant. This has been both emotional and physical. She has been increasingly "unavailable" for long periods of time, and has stopped inviting me to hang out with her and her housemates.
Okay, so she got back with you, now she's starting to think the grass is greener on the other side all over again. If she isn't giving you time, that's a really bad sign... Who is she giving time to? Bad timing last time, she might be lining shit up. At the very least, she isn't really concerned about how you feel (as you ask for her time and she denies you).
She is really nice, sweet, and polite to everyone else I've ever seen her interact with, except for her mom and me. She has a very on/off relationship with her mother/ family in general btw. She will answer in curt, clipped tones and practically chop your head off if you ask an ill-conceived question (ex. hang out this weekend? - NO I ALREADY TOLD YOU (several days ago) I WAS COMPLETELY BOOKED (when she's not) STOP BUGGING ME). This isn't just about hanging out though, it's about everything-- to the point where the only time I can have a nice conversation with her is in front of her friends (she doesn't usually do it to me in front of them, or at least as much-- even given the same conversation topic.)
Not a doctor, but this almost sounds BPD. That, or she doesn't respect you at all.
I have been my usual self- complacent, helpful, I do chores for her at her house, bring her food, am there for her whenever she needs to talk to someone (she'll call me, ask for assurance about something (appearance, fitness, other interpersonal relationships, then neglect me afterwards). I seriously cannot emphasize how accommodating I've been and how willing to compromise/ change I've been in order to try to make everything work perfectly for her. The only thing out of the ordinary on my end is that I took way too many responsibilities on this semester and am going to fail a class. I'm not sure that this is the main culprit though because this behavior has been going on since January and I only told her a week and a half ago about the class. Still, she really values school (as do I). Noted.
Your putting in all this time and effort on her to the point that you're fucking up your own future. And why? She isn't putting any effort in.
(she'll call me, ask for assurance about something (appearance, fitness, other interpersonal relationships, then neglect me afterwards)
Why is she neglecting you?
I stated that I really like to hang out with her but she's made it very difficult, and mentioned that I'd like her to be the one to bring up hanging out sometimes and to try to be a little bit less snappy towards me when we talk. She brings up my grades and makes me feel guilty about myself, and I never get an admission/ agreement to change. I message her later today asking what her plans are for the night and I'm excluded again, even though she's living with these people next year (so its not a "I never see these guys give us time alone") and I've hung out with them quite a bit/ it's not weird me being around.
Once again, you're giving her all this attention and time and making yourself vulnerable by telling her your needs, only for her to not even give a shit about you or your needs or anything about you. Deflects all that shit right back at you in the form of disappointment of your grades (you'd have baller grades if you weren't putting up with her, but she doesn't care about that).
I asked if I could just sleep over afterwards, even explicitly stated that I was OK with just sleeping- she ignored me/ changed the subject twice.
More deflection and rejection. She knows it makes you feel like shit, it is easy to establish that she really doesn't care.
If it was only one night, I'd chalk it up to her being in a bad mood or something-- but it's ALL THE TIME and if she didn't change/make some effort after we had the conversation, what makes me think she'll ever change?
Chances are she won't. She's been doing this since before October.
I was thinking I'd give her two weeks to prove that today was just a fluke before I make the break. I didnt tell her I was thinking of a break because I don't want her to fake it. I want it to be real, or it's not gonna last.
Today wasn't a fluke, the past X months weren't a fluke. It's been going like this since October. Sure, you guys have awesome time together some of the time, but it's a consistent amount of shit you're putting up with over a long period of time. It's hard to look at it objectively because you're only seeing all the good stuff (ask yourself, why do you love her? Do you love her and everything about this relationship, or do you love the concept of maybe having a really good relationship with her? Because right now, what you have isn't matching up to what you want, so those are two separate things you are dealing with)... A lot of this stuff isn't good or healthy. You want it to be all good, you want it to change, but it's not changing, it hasn't been changing, and it sucks.
Tl;dr: I am madly in love with my girlfriend. She has been mean/neglectful towards me though, and I am finally fed up with it. Is breaking up with her after 2 weeks the right move, or should I talk to her again, this time giving an ultimatum?
You need to really dig down deep and figure out why you are so madly in love with her. And it's difficult, because you're right in the middle of all of it, you can't remove yourself from it all and look at it for what it is. But really, think back on your life and all the things that really mattered to you in the past that are nothing to you right now. All your old flames, all your old friends, all your old hobbies, at some point in your life they were monumental, and now a lot of them are just emotionless little flits of memories in your head. That's what time and distance does to a person and the things they get attached to, and you can't really do that now, but really, right now you are probably leaning on her so much for emotional support and valuing her validation of you so highly that you're overlooking all of the bad things, or trying to play them down, and you've got so much going on in your life (school and work and all that) and it's all suffering because you're chasing this carrot on a stick that you're probably never going to catch (the relationship you want with her but you aren't having right now, because of all of the shit).
Sometimes things don't work out, sometimes all the investment makes it feel worthwhile, but it isn't ever going to hold together, and you'll never know until you separate yourself from it and look back on it a few years down the road and think "what the hell was I thinking dragging that out?"
Yeah, if I were you I wouldn't even wait 2 weeks. You're 20. You're young. You're going to have so many relationships that by the time you're 30, you won't even remember the majority of this. You won't even remember why you loved her in the first place.
And I'm not trying to convince you that this relationship is horrible or that you should leave, you need to come to that conclusion yourself, otherwise you might never leave (and she'll probably leave you again).
And it's not your fault. People are different. Chances are you are a well-adjusted and adequately awesome person with interests and hobbies and you can find a relationship that is awesome with someone that sincerely wants a relationship with you. None of this is really your fault if this shit falls apart. If this falls apart, it's not a personal failure on your behalf. The world is full of people that appreciate you, and it's also full of people that don't give a shit about you, and the more time you spend spending around the former, the happier you will be.