Hmmm... Tough Situation... Here is my uninformed analysis...
I think that while you need to distance yourself from your mother a little bit, because obviously she isn't too caring, you should make sure that it doesn't escalate to you ignoring her for a couple of years like Princess_Peach suggests.
Basically:
1) Your mum was too possessive and wanted you around her at all times. When she saw this wasn't going to happen, she threw you out, probably with the hope of you begging her to let you back in, and then controlling you. (IMO)
2) You left your house, in the most humiliating way, being degraded (i.e. you leaving the house was less important than everyone sleeping) and left out on your own without a reliable source of income, without a roof above your head and with your university on your mind.
3) You spent a lot of money on accomodation in a hostel and moving into a student hall at your university, without much notice and without her caring about you, or calling you. She clearly didn't mind you suffering a bit.
4) You repaired your relationship with her somewhat, but spent more of your money on her, getting yourself further into debt. You made the effort to repair the relationship with your money. Did she? Now if I was to speculate, I would say she knowingly got you into more debt to increase contact with you and/or your dependency on her for the money. (hope I'm making myself clear)
5) She suggested that you should not spend Christmas at home. If I was to make some more crazy speculations I would say that this was like a "taunt". She is basically saying, IMO, "Look at you now, I bet you wanna spend Christmas in my house, You'll have to work hard for it!"
6) She is your Mother.
So, what should you do? Your objectives here are to:
1) Put your Mother in her place and make her realise that you don't need her
2) Not break contact with her
3) Make sure your other family gets to see you on christmas
First, some comments. She threw YOU out, thinking this was just a little game she was playing. (IMO of course) Or maybe she was mad and didn't think about her. Regardless, let her know her actions will have conseqeuences. Never again spend money on her, and do not move back in, ever. She made her choice. It was humiliating for you, and painful. Don't do more harm to yourself by moving back in. Also, moving back in, will give her back a certain amount of control over you (i.e. she'll be able to threaten you with throwing out again). So, never move back in and do not spend money on her.
Now, about christmas. My suggested course of action would be:
1) Do not spend Christmas at home. Let her know that you do not need her and that you can call the shots, and that if she says anything that you consider to be too daring you're not afraid to pull out. Plus spending christmas in that environment will just ruin your Christmas spirit.
2) Don't speak to her for a while - her actions have consequences - she threw you out, she doesn't spend money on you, she is rude to you and she spent some of your money. She can't just expect you to go back to her at her request!
3) Come to your home, for a day, a week or so before the Christmas period. Talk to any family you have there. Talk to her, but remember, since you are on your own at uni, you don't need to take any flak from her. Stick up for yourself, and walk out if anything escalates.
4) Talk to her from time to time but not too much. Try to sound as if you don't care about her too much (don't let her think you're dying to get back to her).
So, in effect, don't spend christmas at home, show her that if she doesn't want you - you're not dying after her either, and if she doesn't call, you won't either. Try to spend at least a day with your other family, and talk to her after that, but just a bit.
IMO, and I am no psychologist or whatever, I think that this is all about her wanting to put you in her place as a person who has to follow her command. She wants you as hers (as in always with her) and you don't want too much of that. So what you're fighting for is for your status as a person who isn't under her control, and as long as you let her think or feel that you are dependent on her/care about your contact with her, (by moving into the house, hence being financially dependent, or spending money on her, hence being contact-dependent) she will have control. Make sure you win!
Keep your respect, and make her earn hers, and if she doesn't, she's not worthy of that much attention.
Michail