PS3 account change
To Log off your current user account, simply go to Account Management under Playstation Network press triangle and choose sign out. You can remove the saved password and it won't sign on to your user afterwards.
You can log on to the same PSN account on different users, a user only separates media and saves but account data such as address and billing history is saved per account, therefore if you wish to remove your account from your daughter's user, you can do so without her losing the saves.
If you wish to copy her saves to a different system user, you can do so by by using the Save Data Utility under Game, note however that some game saves are locked to a single PSN account and cannot be copied. In any case, trophy progress will be disabled when playing a save copied from another account
More info on account, sub accounts and users can be found here