Yeah, she does use the kids as a shield, doesn't she!? And, you come up looking like the bad guy if you say 'no'. I found, in the end (after I went through the begging and pleading and logical arguments --- ugh) that distant and friendly worked for me. So, perhaps ask her to stop inviting you to meals, especially, in front of the the children.
And ..... GAL! Find something challenging to do, perhaps, like Toastmasters or something like that --- a new language or something physical, like going to the gym (well, I did, anyway LOL) I was one busy girl!
Me:57 H:52 M:28 Got another lawyer last year and filed. D35,S/D twins28,D22 EA4/04 End? Who knows? "Life is like a mirror. Smile at it and it smiles back at you." — Peace Pilgrim