Man, hopefully you don't take her back. You sound too calm about it like you're willing to 'try again' with her. Remember, once a HO always a HO. Be very thankful that you didn't have children with this woman which would preclude you from walking out of her life for good.
While it sucks to find out this way at least you now know. Make copies of her inbox/sent items, like others said record each phone converation and always have someone with you when you deal with her or do it in a public place.
A guy who works for me had a very similiar situation. He and I had been traveling for work and we ended up fling home a 1/2 day early. I dropped him off at home and hadn't gotten 5 miles from his house when he called me to come to back that he needed help and hung-up. Thinking he locked himself out or somethin I turn around and pull in his driveway. He comes out the front door, white faced - hands over his head and ANGRY. I ask what's up and he said his wife (Cary) was in bed with their neighbor. He tells me to follow him in the house and stay cause he already pulled a knife out of the butcher block found himself standing in the hallway with it and was seconds away from the gutting the guy. Said he didn't even remember grabbing the knife. He's a big-o boy too, the neighbor guy was this puny little dude who wouldn't come out of the bedroom.
Walked in and there's Cary standing in the hallway holding her shirt in front of her with absolutely no clothes on screaming 'No, No, No' at the top of her lungs. Didn't even notice me standing 5 feet in front her she was so freaked out she was caught. My guy told me to go in and get the asshat that was still hiding in the bedroom. I walked in and the guy was dressed and was ready to puke on the floor. I told him that he is going to walk out of the room and go out the back door. He kept mumbling that they were drunk and didn't mean for it to happen. I told him to shut his mouth, look at the floor and walk out, go home and lock his door and to not answer it if my guy came over to 'talk'.
My guy kicked his wife out with just a shirt and jeans, her car keys and purse.
Long story short later that day she went to police to file an emergency protective order saying he hit her and the cops came and got my guys gun collection and served the EPO. I was called in the next day to go down to the courthouse to give my version. It was a full year before they returned about 5K worth of firearms.