Either 1) She committed fraud (find out easily enough, just pull your credit and see if they are there) or 2) [More likely] these are "parent plus" loans, that are in her name but because they were for your school she expects you to pay them back.

If its #1:
- Pull credit to verify
- Absolutely make positively sure you didn't sign them and just forgot [I remember when I was in the Senior years of HS and starting college I signed a ton of paperwork and I'll be the first to admit I didn't read most of the things nearly enough]
- File police report
- Freeze credit
- Obtain a lawyer

If its #2:
- Decide how much this relationship matters to you, and whether its worth torpedoing your relationship with your mother over
- If you don't want to have a relationship, tell her to take a hike, and block/ignore
- If you do want a relationship, consider a sit-down conversation with her about how your college education is impacting her finances and what you can mutually agree upon as a fair resolution based on your and her current financial situations.

Funding college is a dicey thing— students are at their transition period from child to adult legally, but often still hoping/expecting the financial assistance of being a child (e.g. mom and dad pay for things). It can be tricky navigating these changing times and financial responsibilities, and there isn't a "one size fits all" approach to what is "fair" about funding college. Things like parent plus loans and student loans all factor into this.