OP here. Thank you.
I think what threw me off was that the other mom insisted it wasn't pink eye. In retrospect, I'm 100% positive it was pinkeye. It followed a cold, eyes were very red, drippy, friend was cranky, etc.
Can anyone offer specific dialog advice? ""sorry, but we just can't afford to get pinkeye." from a PP is very useful, but what do I say when friend's mom says "it's not pinkeye. i know this because [insert nonsensical reasons]."
Also, I really do feel bad about inconveniencing the other mom, so I don't want to sound flip. ""Yeah, I wish you'd have told me before getting in the car and driving here. We'll have to reschedule after your DD's eye has cleared up." And this sounds kinda flip to me.
I'm not used to this kind of thing, and it makes me cringe. 12:49, thank you. I'm glad to know I'm not the only one.