Birthday party clash

[belleville42]

AIBU to tell other mum that she's being totally ridiculous in asking my dd to choose which two best friend's parties to go to?
Background: Mum 1 has party 3pm-8pm. Mum 2 has party between 4pm-6pm. On the same day!
Asked Mum 1 if it was ok for me to drop dd off at 2.45pm and pick up at 3.45pm for her to go to other best friend's party, and then bring her back for 6.15pm for the final part of her chid's party.
Mum 1 wrote back and said dd has to 'choose' which party she goes to!
This is ridiculous!! Has she never 'party-hopped' to be present for good friends? I know I have. So, why should it be different for nine year olds?
Mum 1 is 'centre of the universe type'; Mum 2 is chilled, laid back and understands life (my good friend obvs!)
Concerned as I have to break the awful news to dd and it is going to be upsetting as both are her good mates. She wants to go to both.
So: Do I just turn up with dd at 2.45pm, take her off at 3.45pm for other party, and then bring her back at 6.15pm?

AIBU to just tell Mum 1 she is being ridiculous and needs to chill? And take on the onslaught from her, or just not pay no heed to her email and just do what is best for dd?
After all, Mum 1 can't refuse entry with an adorable dd standing in front of her - surely?
Why are people this way? Am I missing something? AIBU?

If you want to do both parties, do the 4-6 one then the other one 6.15 to 8. DO NOT leave one then return later, it's the worst bad manners and if I was Mum 1 I wouldn't let you back in: I doubt that she'll find your DD "adorable" enough to disrupt her own child's party.
You sound as if you think your DD will be the most important guest at these children's parties but I highly doubt that that's the case.

What a great thread!! As well as teaching your DD to be kind and loving to her friends, you also need to teach her that at times she has to make a decision and sometimes that means letting someone down. They are 9 and genuinely will not be bothered but you do need to choose a party and apologise to the other mum asap. Party hopping is incredibly rude so choose. If you want to show the love for both friends then buy a present for both and arrange another date to meet the friend whose party she does not go to.

Yes that's all that matters, that the ops child is happy.

I think the party hopping thing is weird and ill-mannered (unless you are a student or some sort of 80s throwback). It feels like arrogance and self-centredness on the part of the 'hopper' who thinks that their presence is an essential component of a party.