How can I take my name off a mortgage I got with my ex while we were together. She keeps using this to keep me around but I just want to get off it.

Last year my ex and I got an apartment in Manhattan. We deiced to get a mortgage on the house even though we weren't married or in any form of a partnership besides bf and gf. Now that I broke up with her she keeps using this to talk to me. What are my options to get my name off the mortgage since I've already been out of the apartment for half a year yet I still pay her since I'm worried she wont pay the mortgage if i stop talking to her.