There is so much incorrect and bad legal "advice" in this thread it's amazing.
Because of the nature of adultery most states have presumption law that makes it do you don't need actual evidence of cheating, you can file for divorce on grounds of adultery with circumstantial evidence, and judges make the presumption unless she can rebutt it.
I'd subpoena all her phone records and text content from phone company, and Facebook, and everything, likely to find more circumstantial evidence.
If a client came to me and said what you said, in my state (which doesn't apply to you) I'd easily have a divorce complaint drafted that day on adultery. Many states apportion differently for fault divorce - contrary to what people are saying.
Lawyer up, and best of luck finding a true woman. Sorry to hear bro.
These are my Internet comments and do not constitute legal advise.
