If it's normal for you to go over and cook, that sounds like a fine thing to do. If you can find out ahead of time if she likes the idea, and if you can do it with NO EXPECTATIONS, just a friendly happy-go-lucky kind of day, go for it! Doing it along with BIL and MIL might be a good way to dilute its pursueyness (!) as long as BIL isn't going to be all mushy and kissy with his w.

I wonder if I'm getting any special treatment for Mother's Day. Probably not...

Adinva 51, S20, S18
M24 total
6/15/11-12/1/12 From IDLY to H moving out
9/15/15-3/7/17 From negotiating SA to final D at age 50
5/8/17-now: New relationship with an old friend
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Happiness is a warm puppy.