So, let me guess. You are scared OM is coming over to the house and that is why she reacted as she did about you going over there. Thus, you bring up OM because you are scared.
If that is accurate: (1) Very likely OM is coming over to the house, (2) if OM is coming over to the house, W will almost certainly lie about it if you ask her and she certainly will not volunteer the information, (3) your nosing around and heightening her feelings of guilt over it will bring them closer together and cause her to avoid you and intensify her negative feelings toward you.
Why not just operate from the assumption that her A is in full gear, a PA, and she is pretty excited about it right now? Then, you can stop worrying about it. Assume the worst so you don't have to obsess about it. Then, settle in to DB or not.
