Just caught my girlfriend cheating

I am devastated and need some advice... Just recently I started seeing a change in my spouses habits and her starting to hide her cell phone, and leave it in her car. She was spending more time in the gym and not calling me on her lunch breaks... So I found this app that I secretly installed on her android cell phone called cell phone sleuth. I put it on her phone secretly and I was able to track her calls , text messages, gps locations etc. Come to find out that she had stored some guys number under one of her best friends names in her phone. She has been calling him while at work, and texting him pictures of herself, and everything imaginable. I am so devastated and don't know how to approach her on that she is cheating and how i know. Can someone give me some recommendations? I obviously am not staying with her....

Thanks,
Rpet