I've had something like that before whenever one of my cats was at the vets. It was always my female cat. It was as though they didn't recognise the other cat. I believe it's the different smell from the vets. It's almost like introducing a new cat into the household. I'm sure Mum will settle down after a while and even 'tolerate' her daughter. But, as you said it's also a part of growing up.

Good luck
Mary