One of DC's best friends' mums is prone to sending me long and rambling messages. I can't say too much about specifics as it would be outing, but as an example she would start with a question about something the kids did in school that day (they're in Year 2), followed by a long and at times incoherent message about some of her own personal issues.
It's gotten to the point where I now ignore/don't reply to some of the messages. I also don't really wish to speculate on any psychological or mental health root causes, as I really think it's none of my business.
As I am not often the one doing the school drop off/pick up, there is a lower (but not zero) chance of an encounter in person - I'd just go "ah sorry I forgot to reply to your message" if asked.
However I can't help but feel discourteous /flakey in doing so (as I wouldn't do this to anyone else). DC is getting fewer playdates with this friend than they'd like, as a result of my aversion to communication with their mum, and I feel bad about it for the kids . AIBU? Should I be approaching this differently?