A lease is a contract and I am betting that you are both jointly and severally liable thereunder.  That means that both of you are responsible for the full amount should either of you default and not pay. So if you can not afford the rent alone I would approach your landlord about your getting another room mate and consenting to it in writing.  Otherwise you can pay all and sue her each month for her half.  But it does not sound as if you will get anywhere with that.  Good luck.