It always amazes me how on MN, no one is ever willing to give just a little bit, because everything comes down to is right and that's the end of it.
Everyone is constantly moaning at how nobody is never ever shown kindness or empathy, yet the norm is that as long as one can prove they are right, they are exempt from sharing any kind of kindness.
Of course the woman was in her right. Not one bloody person would be stupid enough to argue it. Yes, the mum shouldn't have given her a mouth full.
I all likelihood though, she assumed as you would, that the seat was free, and even doubt that the woman was telling the truth about having booked both because who has ever come across someone who does?
We don't know the circumstances. Maybe that mother was especially stressed, maybe she wanted to book both seats but she was too late and there were none left available, which would be especially frustrating. Maybe she could only afford one seat.
My point is that sometimes, you gave to step away from the primitive satisfaction of just proving someone wrong and getting some enjoyment from the outcome. Sometimes, there are ways to give a little and find that it pays off in other ways.
It certainly works for me. I have regular tales of giving a bit even when I don't want to to find out that not only the other person is grateful which makes me feel good but are able to give something back, in as a basic way as to provide vaulable advice about matters that help.