OP here.

Thank you all for responding.

We never discussed this.
That day when I texted my boss and said that I wouldn't be in the area until 4, I also told her that DD said they weren't going to run that day for whatever reason.
MB responded with something along the lines of never mind then, it was probably just P.E. and it's over anyway.

When I picked up the girl that day, I asked her what she ended up doing. She said they did have to run for a bit, but she borrowed shoes from a friend.
I told her I was happy she was able to run and I said that while sometimes I stay at her house during the day, she needs to double check in the morning to make sure she has everything she needs for that day.
I told her we could make a checklist and put it on the fridge and see if that helps.

OP, an update?

Anonymous wrote:

Anonymous wrote:Forget the fact that the kid is irresponsible. That is their problem.

Decide what your rate is for doing a middle of the day errand. $20? $40? $60? Your time is valuable. Tell MB that if she requires your services during the day, it will cost $x for you to drop everything you are doing. Your time is NOT free.

Shes sitting at home watching tv or sleeping, she can't help out the woman who pays ALL OPs bills once in a while? Stand your ground OP and don't help out, you'll be back here in a week complaing about how your heartless MB fired you when you have always bent over backwards for them @@

If your boss asked you to come in after hours to bring something they forgot ... Would you? I sure as heck wouldn't.