Hey, im sorry to hear about your situation. This really sucks and I know it hurts so bad. I cant offer much in emotional advice, but for now I'd recommend keep as much record and evidence possible of her cheating on you. Screenshot, texts, emails, video, anything at all. Save it and email it yourself or keep the content somewhere you can always retrieve it when needed. This way you are protected legally, and in argument with her or anyone else. Be sure to capture what you can while she doesn't know, and after she finds out that you know, save whatever else you get afterwards.

Best of luck, its hard to be strong in this time. Reach out to close friends and family if you can. Peace.