I went abroad and subleased my room to another girl and had her sign a sublease agreement. She was supposed to say for 4 months (I will be back in June to take the room back and stay until the master lease ends at the end of August) but ended up only staying for 2. The months that she stayed for she paid for and she wants to pay the utilities for the month that she lived there too. I had her pay a 100 less of the rent since she was subleasing and I paid the 100 instead. She claims that the sublease agreement was invalid and that is why she moved out. Our landlord knew that she was living there but according to the master lease we were supposed to follow certain procedures that we did not such as her submitting an application and deposit to the landlord. I do not have a written agreement from him but I did get her to sign my sublease agreement which I can get the landlord to sign after the fact. My landlord is holding me responsible for the rent. Also, she lives out of state. Can I sue her for the other two months? Do I have a valid case?

You are responsible for the rent to the LL. If your sublet was illegal then you have nothing to sue for. Did she and the LL have some discussion about not following the lease?

No as far as I know there was no discussion. Can I get written confirmation from the landlord now and provide it? Or have him sign off on the sublease agreement now? The problem is that she has a copy of the sublease agreement as well but that does not have the landlord's signature on it. If I have a copy of the sublease agreement with the landlord's signature will her copy matter?

No, getting a signature now is after the fact. Apparently, from what you are telling us, the sub lease agreement was flawed since you were violating a term of the main lease. I would not waste my time trying to sue her for 2 months rent. She apparently knows the sub was no good and that explanation will sink you in court. You could get that signature and try to get a new tenant if you want. For now you must pay the rent on your own.