My MIL hardly ever respects boundaries, and when called out on things not putting sunscreen on flat out lies (I was looking at the sunburn on my kids!) but at the end of the day I rely on her in school holidays and whilst I detest some of the things she does (crap food etc) I've had to let it go because I need her.
My mum took DD to get her nails done without asking me but I am so far from a girly girl that mum probably knew I'd never take her. My mum is much more respectful of boundaries and if she isn't sure about something she will ring me, sometimes that drives me nuts too.
They both do things that drive me crazy when it comes to my kids, but I know they will care and protect them and never put them in harms way. There's not many "firsts" I can think of other than a haircut that would really upset me, like I said I rely on the help so take the good with the annoying.