Here's a quick question. What do you do when you've asked WAW not to bring kids around OM, and yet she does?

This past weekend, W and kids went to MIL house, where W dropped them off and went to a Memorial Day over night party. Then Sun came back up here w OM to another get-together, had him stay over at her apt and then on Monday went to another gathering in Saratoga, w OM and kids, in which they didn't get back until 10 pm last night, and D6 informs me 'Kelley stayed at mommy's house last night.'...

Would like thoughts on what to do...Thanks