Pathos my friend, or perhaps pathos's girlfriend, let me share some incite with you that I gathered through some pretty horrific personal experience.
See, years back before my current life as a hermit I had a girlfriend who I see shades of yours in. Her obsessive intrusions on your privacy could mean many things, things I can't guess without seeing you in person, but more then likely its one of these two: She's either so entirely obsessed and dependent upon you that she jealously seeks to destroy your other relationships or she's feeling guilty about her own infidelity and taking this guilt out on you by subconsciously assuming that you must be cheating too. Theres the chance that she's just extremely controlling and manipulative but thats something I hope you'd notice on your own. Considering her post of you being a serial cheater I'm leaning toward it being entirely possible that she's just abusing you to feed her own insecurities but once again, I can't be sure.
I recommend you two sit down and try to calmly talk out exactly why she feels the need to check up on your private dealings and see if there's a way to make her feel at ease enough to stop doing it. However, if she simply refuses to stop and continues to invade your personal space then I suggest getting out before you're in too deep.
Otherwise you may end up like me, dropping off the map, moving to another state and still being stalked by a bi-polar nutcase.