Ex-Tenant vs Ex-Tenant

[czz7661]

Any suggestions or help would be very much appreciated. So the back story is my ex and I lived together in an apartment with one lease two names so basically they would only accept one rent check not two. Living together became very difficult so I moved out in december and continued to pay rent there until February when her friend moved in and they both told me I was no longer responsible, yet I stayed on the lease. Her friend got sent to the airforce in April and I picked up rent for may. Fast forward to July, my ex sends me an email saying that the check from march from her friend bounced and she never saw a check from april and that I owe her $800 for this. I feel that I shouldn't be responsible for March since she allowed her friend to live there, but april is another story, but I'm usually wrong when it comes to these things. The ex said she was waiting on the girl in the airforce regarding the money but I have a feeling this is going to come back to me.