.. So because you 'caught her in a lie' .. That it somehow entitles you to control even her phone .. Sounds like you got bigger problems than just a phone app.
Me and my girl have boost mobile...and I want to see her text pictures and texts. I caught her in a lie before..so now we have Boost,, how can I do that?
So what I read between the lines is, you don't trust your girlfriend and are now looking for some way to justify breaking up with her. Just skip that ugly and demeaning (for both of you) step, and break up now. Why cause more grief than there all ready is?