Mixed relationship with my DM, used to be v close as I was growing up but more and more things happened and I also realised other things she's done I used to think we're normal and we've kind of grown apart.
She has in the past exploded over small things, invaded my privacy (read my diary), was quite controlling in general. She tends to read into tiny little details or what I say/do that I don't ever even give any thought. But I've got my own home now, my own DCs etc so I generally just let her sweep stuff under the carpet to avoid her making herself out to be the victim IYKWIM and I've stopped reacting to her rants (not had one for months now thanks to this) and she seems to have cooled off and has gone a little detached.
So here's my AIBU. I see them once a week with DCs (DM and DF), always at their house and we just relax, recently I went over and DM announced we were going out to a restaurant. She didn't bother to let me know the day before, I turned up in dirty jeans and a stretched out jumper, DS was also in some runaround trousers and mucky boots as he always ends up running around in their back garden and jumping in puddles.
Mentioned it to her saying she could have let me know and I would have dressed appropriately, she said they (her and DF) only decided last night and it was too late to text 
I also mentioned it to DF and DBro (teen still lives with them) and they both seemed quite surprised she didn't tell me.
AIBU to think that it's just her petty way and she didn't let me know on purpose?
She always makes a big deal about going out and really dresses up so its not as if she doesn't bother herself.