I dunno... if it is something you pay for, then I think you have some right to snoop. However, unless she's given you an excellent reason to do so (doesn't sound like she is out of control or hiding anything dangerous from you), you don't want to violate the trust and open-ness you already have.

For my parents, as long as you were underage and in their home, 'privacy' was not something in their vocabulary, lol.