I agree with AnnieBrooke that you need to distance yourself and let her know that when the baby is born, you'll need DNA testing. Until then, try to be calm, what will be , will be. Whatever you do, you must stay in school and finish your studies. That should remain your priority.
If you had sex on December 10 (I realize you say "around" December 10, what does that mean exactly?) and she told you on December 17 that she was pregnant (how did she tell you this, by email? Because you said you were gone until January 10, so it doesn't sound like she told you in person) -- anyway, 7 days is a very short timeline for discovering a pregnancy. I would explain that if you are the father, you will be confirming of course with a DNA test when the baby comes, and in the meantime you would appreciate no contact because to you the story is not adding up.
To add: why do you care if you undermine her "trust" if you are trying to fade her out of your life?
Didn't you just post here using another name?
How is this person an "ex" if you just met her and had sex with her? Just wondering.
Anyways...........
It doesn't matter if she has psych issues or physical issues or any of the other insignificant things you've mentioned about her..........the FACT is YOU slept with her without using protection and WITHOUT knowing much about her and YES she may be telling the truth, HOWEVER, no one here can tell you if she is lying or not. Time will tell.
In the end it's about what she wants NOT you because it is her body. You can't demand or force her to have an abortion because you are a poor college student who is not emotionally or financially ready for a child.
Before getting all worried about the "what ifs" WAIT until she produces a baby. Meanwhile, cut all contact off with her AFTER telling her to contact you when the baby is here. No one can pursue legal action against you for doing that.
Everytime you take a woman to bed there is ALWAYS a risk of pregnancy whether there's a condom involved or not, so if you are poor and not ready for child then conduct yourself in manner that reflects that.
Only time will tell if She is pregnant
that being said
In this day and age, Men are responsible for Their own sperm. That translates to : don't ever, ever, EVER have unprotected sex.
and
because there is a certain amount of failure rate for every/any birth control method, don't have sex with someone You are not ready/willing to make a Baby with - it's as simple as that. This is good advice for Men as well as Women.
This would equal no 'unwanted' Babies. What a Wonderful World that would be.
........just saying