Well my guy cheated on me...

Cheer up and have some ice cream https://lh6.googleusercontent.com/-YxZ4ilO9-u4/U-k-a7_RUeI/AAAAAAAAFMg/0aR41OUentA/w672-h1023/Render_luka_megurine_by_beatomegu-d462fti.png

Stop white knighting. She did wrong, then was an asshole afterwards. She deserves what she gets.

She's a drama queen anyway. Only white knights are talking to her. http://i0.kym-cdn.com/entries/icons/original/000/011/869/internet_white_knight_colored_4350.jpg

Relationships obviously have to be built on trust and they're not gonna last very long if you can't trust each other. That said, if you have reason to believe your partner might be unfaithfully I don't think it's so unreasonable to look into the matter. If a wife found lipstick on her husband's cloths she might hire a pi to investigate the guy's activities to see if he's cheating, and most people wouldn't think she's a bad person for doing that. The thing is there's a bit of a difference between seeing if someone is unfaithful, and pushing them into that situation. Of course as many have stated I think the outcome here was to be expected. If your relationship isn't going so well, and all of a sudden a girl comes along to tell him everything he wants to hear then one can easily guess what's gonna happen. I think the proper response to a waning relationship is to try and fix it, not put extra strain on it. If the fire's dying out try to reignite that spark between you two, don't just pour water on the dying flame to see if it keeps burning. It's as simple as just doing things to keep them interested in you, and if they're interested in you they'll do more things to keep you interested in them..

I have no further relevant input to give to this situation. I'll just agree to what neet-one said. baiting someone into unfaithfulness is bad. but biting the bait is bad too. I hate people who play games with relationships ;/