IF this is really your GF you are worried about and wanting to see then just fucking talk to her. like another said, a relationship is broken without trust and what's the point of constantly worrying. IF you talk to her and you honestly think she's still lying then break up with her. stop being a bitch.
Ok Im going to give you some real advice are you a man or are you a fucking bitch..... What are you like 15 or 17 dude One ASK HER confront her about it. Two look for differences in how she acts in certain situations. Three Dont fucking confront her she will think your insecure and dump you. Sorry thats the other side of me. Dont listen to that side.