statue of limitations

i have a private student loan which orginated in 2006. i live in texas and the loan comes from Pennsylvania. what is the statue of limitations. I have a cosigner which is my daughter on this account and originally the account was in a hardship forebearance. i ran into hard times and the account was placed in collections ruining my and her credit. how can i get her off? they keep giving up the run around-they told her that the account was in her name when she tried to pursue it and on yesterday, now im being told that i was the primary borrower. i also was given a repayment plan which i have followed to the letter but i chose to pay more and on this morning, she was told that we need 48 payments before she can come off, payments needed to be automatically debited and that the payment i paid wasn't honored. HELP!!!!!!!!!!!!!!!!!!!