Um... HELLO! When a mom with kids goes into a stall it's ALMOST going to take as long as an elderly person.
She should be grateful your daughter isn't 3... And both of you going (her likely then needing to poo, OR using both stalls.
"No! I can't pee in the sink while changing her diaper, because its too tall off the ground, nor insert this tampon while she's pulling up her clothes. Nor get the preparation H on right. Thanks for the offer, though!"
The above is actually something I smilingly shouted out 8 years ago (but used the pronouns "he"/"his"), when someone was being cranky. Ditto, standing diaper change and mama peeing multitask. I wasn't on my period, and didn't have hemorrhoid... But, since she was trying to shame me, I decided to be shameless and give her something to think about.
I have this filter problem, you see... IRL words just fall out of my mouth while I'm grinning happily away.