Sure, one could argue that guy bought the computer, and therefore he's entitled to place on it whatever software he sees fit, but girl can also argue reasonable expectation of privacy.
Usually people in situations like that are grubby drunks and drug addicts. Everything is mutual, esspecially domestic violence. In the real world things aren't like detective comic books or crime noir novels where some trench coated P.I. helps out some pretty damsel.

More than likely, none of these people have a single respectable attribute to themselves.