My MIL called my son "my angel" which made me cringe.
1) he wasn't hers
2) I have friends whose babies have died or been born dead and they refer to them as their angels, so to me a child referred to as an angel is dead
3) she might also have been referring to children who are always good as being angels and that's really an unreasonable expectation
which could cause problems.
So, I explained those and she stopped.
Your poor MIL. The "my" thing probably only meant "my grandson", which he is! My mum calls DS "my boy" and I think it's quite touching as it shows how much she loves him and how attached she feels to him. He is hers, in a way and I'd feel just as happy with MIL saying that too.
Am pretty sure she didn't mean that your child had to behave perfectly at all times either, it's just a term of endearment FFS! My mum always used to call me and my siblings "my angel", it was just like saying 'darling' or 'sweetheart'.
As for the "angels mean dead children" thing, yes bereaved parents do tend to refer to their children as 'angels' but so do lots of parents, grandparents etc of healthy, living children. Each to their own though.
I just can't believe you actually stopped her from using a well meant, affectionate term of endearment to her little grandson. Did you really tell her that she couldn't call him "my angel" because he wasn't hers??
Sometimes Mumsnet makes me dread becoming a MIL 