DSis and I were extremely close to our mum, but she really overstepped on this one thing. When DSis was giving birth for the first time, our parents were in the hospital waiting room (they’d been having dinner together when her waters broke).
It was a quick labour, and when DBiL popped out to say it wouldn’t be long, my mum followed him back into the birthing room, uninvited, and was there for the last 15 mins as nephew was born.
Everyone was preoccupied, obviously, and it was too awkward to ask her to leave again, so no one said anything, but DSis always felt she kind of ‘took’ something from the moment. She made it about what she wanted rather than what DSis and her husband wanted, and instead of being something private and special, it became a story my mum liked to launch into as a proud new gran - even though it wasn’t hers to tell.
We loved our mum dearly and she was a truly wonderful grandma, but in that moment, overcome with excitement, she was selfish and intrusive.
If you and DH don’t want your mum there, be very clear about your decision up front.