Not sure what country OW is in, but do you think this could be a scam? I mean, she hasn't slept with your W (even though they were together), is "saving herself" for marriage but isn't bothered by breaking up your family? Is it possible she is just looking for a green card? This scenario has surely played out in a lot of heterosexual affairs here. Sometimes the OP has several people on the line, just waiting to see which one will come through with a marriage proposal and green card status first. OR they're just scamming money, getting the WAS to send them money for bills, airline tickets, etc. , milking it for whatever they can get until the WAS finally figures out they've been had.
Is OW from a country where this might be likely? (Seems like Russia, Asia, South Africa have been the places I've seen on this board. One guy left his wife for a South African prostitute he met online - he married her and brought her to the U.S.)