Revoke Financial Obligation Consent

My mother was taken to the hospital after I worked a 14 hour shift and in the ER they jammed a bunch of papers in my face while I was tired and not thinking. They described it as medical consent forms but one of them was assuming financial responsibility for all her medical bills. Long story short I have a checkered past with my mother and I'm the only family she has that's willing to even go to the hospital with her.

The question is, can I revoke my financial assumption of responsibility after the fact? Even if it impacts other consents or whatever. She only has Medicare and I don't want to be saddled with her debt. I live in Houston, Texas and have medical and durable power of attorney to help her make decisions but not eat her debt.