She's using the kids to try and hurt you (AGAIN). In this case her trigger was OW, that disclosure clearly angered her.
At this point I would suggest sharing all that info with your solicitor and see what their advice is.
I have done some dating, but not when I have the kids. My W has had her OM around the kids and it really upset them because they still hold out hope for reconciliation, and so they see OM as the roadblock to that and they don't like him by default. Granted my kids are older than yours, but because of that I will not expose them to an OW until after D, and even then I think it'll be a long while before I do.
