ipad has one account loged but when starts downloading apps associate another account! Help!

Hi,

Two years ago my girlfriend buyed an ipad with my advice. When starting the ipad i was forced to associate a credit card. Because of this i created an acount wiht my e-mail so that she couldn´t do any purchases with out my knolegde.

Recently i upgraded the ipad2 to the newest ios, and everything went fine. I created a new account for her and cofigured her account on her ipad with no credit card.

The ipad worked for 2 months with no problem, but sudently, with her account loged into ipad, when prompted to update apps the account that appears is mine, in every defenitions i configured his account but my e-mail always appear when prompt to update anything.

Tryed: Reboot; Deleted all information from ipad; Configured her account; Reconfigured her account; Etc. Help!!

With no success!

Can i simple delete my account from Apple?

I would thank some help.

Best Regards

Nelson