FWIW, I am going through my own nightmare with a run away wife but not as complicated as your situation. I have a strong suspicion if you take her back, this issue will come up again. My advice might be to do what others say and step BACK. Do NOT take her back in at this point. Cheating and getting knocked up is life changing. Me personally, I know I could never take someone back and fully love them after something like this. Cheating would end things for me anyway but add in a child....no-go.
I would let her sweat it out. She made her bed. Only issue is if you are married, finances might get very complicated for you because her situation is likely going down the tubes.
