My wife has a history if sexual relations with her mothers new husband (not bio-dad).they continued their?

relationhip til i came into picture. The twwo have been doing it since she was a teenager. she said she was the one who approached him and when i came into picture she said she stopped but he continued to pursue til we left together. her bio-mom knows and never left her husband. her bio-dad knows did nothing either. she has been spending an enorumaous time with her mom and her moms stil spouse (the man she was sexual with since before she was fifteen). She is still overly close to him and now they went on a trip just the three of them to see wifes brother graduate from military. they been gone for 10 days driving spending nights in hotels and now on the base where there are three rooms for the three only. She did not want to take any of our kids with them for the trip. she wanted to be alone with mom and moms spouse. they used to play while her mom was home before and each other almost every night while she lived with them before we left. at first she said it was him then admitted it was her who started it. how can you know if it actually stopped? I still have trouble trusting her and him together and have during our whole relatonship but i do love her and cant nor do i want to control her or her behaviors. Is she still playing with him?