If I understand what you are asking, I think I can answer.

You can have multiple accounts on an android device and purchases from any of the accounts can be downloaded on the device.  So, if you want your device to be associated with say "dad at g mail" and your daughters to be "daughter at g mail", yet one or both devices to also be able to load apps purchased from the other account, that can be done, as long as both accounts are associated with the device that wants to load from both accounts.

As far as the emails being seen/ read, you can sync hers to read only her email.  But, its pretty easy for her to change it to also read yours, and vice versa.

Is this what you're asking, or did i miss the boat completely?