Found out Girlfriend is cheating but she doesn't know that I know?

I found emails that show conversations between my Girlfriend and a guy that she told me about. She told me 6 months ago that he owes her money but he never payed it back. There are emails where he jokes about me and asks her when he can see her again for a good f… She calls him babe and he sends her emails saying "I miss u". I checked her old phone and saw other text messages from asking my Girlfriend when "she can find some time for him"… I put the phone back where it was and next day she took it and now she deleted the text messages… I haven't talked to her about it… Last night she came home at 2am telling me that she fell asleep at her friends place because she had a long day at work. When she left to meet up with her, she had makeup on and her hair was straightened, when she came back her hair was curly (which happens when her hair gets wet) and the makeup was completely gone… When I confronted her she said she would never cheat on me and she is not that type of person. I know she's trying to hide it but she was too late, I found her old iPhone with his text messages before she was able to delete them and i saw the sent and received emails between them… What do you guys think? She doesn't know that I know and I don't know what to do

If you know she's cheating,

Be super nice to her for a few days. Cuddle, hold her in her sleep, and take her out on a surprise date. Mention, but don't keep saying, that you feel bad about accusing her of cheating. Maybe buy her a present. If she's not a psychopath, she'll feel super bad. Do this for like 3 days.

Then, suddenly turn the charm off and act super moody and like nothing can please you and giver her a mean look a couple times. She'll wonder why and, if she is indeed cheating, she'll start to suspect that you know about it and she'll start to try very hard to please you. Do this for 1 or 2 days.

Then, suddenly turn the charm on again and the same stuff as before. All throughout this time, try to collect some evidence. Once you get it, tell her you know she's cheating on you, and show her the evidence. Then, pretend like she doesn't exist. Tell her she means nothing to you and that you don't care about her ANYMORE. If she lives in your place, get a motel room for a couple nights and tell her she can go stay there for a couple days before she finds a place of her own. You might want to call a couple mover guys too. Pay for all of this yourself.

I know some people might think this is weird or cruel, but this is honestly what you need to do. I'm sure you cared about this girl, and she might have cared about you, but that doesn't matter anymore, because she decided that you aren't more meaningful than a "good f…" She doesn't even have the courtesy to break up with you first. Make sure you take all the emotion your feeling and put it all into tormenting her, and make sure you enjoy it.

PS: A bonus would be to find out who the guy is and give him a couple scars, but only if you know you can take him.

Well, it's obvious she's not into you any more. I'd say pack up her stuff one day and leave it by the front door. Let her know you know she's been cheating on you, and with whom, and when, and that you're not mad, you're just very disappointed she would insult your intelligence that way by lying to you and being so sloppy in her cover up.

Then tell her to get out.

Make sure you don't have any joint accounts with her of any kind. Make sure she takes all her property and doesn't leave any behind.

Then block her, and go on with your life.

I got some great answers, I appreciate it. I'm still playing the best actor right now and I mentioned to her that I noticed that she's been hiding her phone from me and every time she puts it on the table she always puts it face down with the display so I can't see who is texting… She said she is not hiding anything… Lol