About To Come Off Of Fmla, Offered New Job, Will I Face Any Legal Ramifications?

Location: Massachusetts

Hi! Thank you for taking the time to read this. I appreciate it.

I (F29) have been working for a local hospital for close to 2 years (not as an RN, I am not sure if that matters, but I do work in patient care). I have two positions in the hospital, one full time and one per diem. On November 6th, I took FMLA (Family Medical Leave Act for those who don't know) because I was just having a really bad mental health crisis and I needed time to get myself right because I was burning out.

My leave is scheduled to end February 19th.

The closer I got to having to go back to work, the more I realized that I really did not want to return to this job because my boss made life difficult for me in all the ways I dont feel she should. She withheld hours, she allowed bullying amongst staff, and she would often make these remarks that felt almost vaguely antisemitic (example, when I put in for my vacation times at the beginning of the year, I was allowed 2 weeks vacation. I put one week in for my anniversary, and one for Hanukkah, and she called me in and told me she'd be denying my Hanukkah vacation because "Christians don't get Christmas off so why should I get a whole week off?" even though I had accumulated that time). During the course of my FMLA leave, she would constantly call me, ask if I would come back early, tell me I "owed it to her to pick up the phone when she called", said my paperwork wasnt in order despite the state government website saying it absolutely was, and anytime I said "please speak to my HR representative about this", she would say that it was just easier for her to talk to me and not them.

I ended up getting a job offer yesterday for a job that is less stressful and pays more, and I want to take it, but I am not sure if I will face any sort of legal ramifications for exiting a job right after coming off of leave. Is that allowed? What can I do? What are my options? Do I have to work "two weeks" before I can start the new job? Please help!!