I don't think there is an OM. Early on, I acted a little jealous and she said that she doesn't have any romantic feelings for anyone, so not to worry. I do trust that statement. She said a couple of months ago that it sucks that she can't ML to me. I always thought that was a weird statement, not sure what she means with that.
Re the knowledge that will taint my W, I did not say much to the in-laws, and certainly nothing that has changed their opinion of her. My W has always been kind of the odd-one out in her family. My SIL is the favorite.
She says she feels like EVERYONE is against her and that she is trying what she thinks is right. I told her that I know that and that I am there for her, to help her.