RTL I think you should decide and let W know right away. As a woman , I know it drives me crazy when my H make me wait and wonder over something, why anger her more. There is no right and wrong and she needs to understand this is a difficult situation for you, so it is hard to know what to do. When you think about though, it can only be beneficial to your D. Even if your divorce goes forward and W ends up with OM, it can only make things easier for D if she sees you can manage to be together when it has to do with her, I know it is terrible for you and not right your D is in this situation , but at least you going to the party might alleviate some of her fears about the future. You were asked to come, b y both D and W so, if you can deal , then go.