Some thoughts:
There is a ton of back and forth already. So I would try to leave it alone and let her process before sending any further info.
I would have have either termed after her text OR said that unless she gives me 48 hours notice that I will be terming due to licensing. And left it at that. But hindsight is a wonderful thing. So use this as a lesson learned and move it on forward.
I wouldn't mention anything about the food being wasted. Your reason should be related to the group (imho): It is too disruptive to have a last minute change of plan. Unless I receive 48 hours notice I will not expect dcg. If she shows up, it will be an immediate term.
I would let the school know that on Tuesdays, dcg is not to be there unless dcm gives them (the school) the heads up. It is too easy for you to be back up with this set up and to have a similar situation again (dcg there unattended).
This dcm needs clear boundaries. I guess, if this was me, I would tell dcm that you will take dcg on Tuesdays with 48 hours notice ONLY. Set a time limit: Sundays by 8 pm. There is an extra charge for this, as well. (I would charge $10 - or whatever fee you feel makes it worth your while). That if there is not proper notice given and dcg shows up, you will have no choice but to term immediately and call CPS (well, maybe that sounds too threatening with the cps). That dcg is to only use the bus stop at your house when she is scheduled due to licensing. So on Tuesdays where dcm doesn't need you, she is not to be there.
But honestly, it does not seem like it is a good fit. I would tell dcm that after reviewing, it is in dcg's best interest to be with a similar age group. And I wouldn't wait until summer. Do it now! It is really hard to do mixed age groups, especially with only 1 sa'er.
Any more sass from this dcm and I would be showing her the door: immediate term.
I would not worry about talk. I think it would reflect poorly on her, rather than you, anyways. I live in a smallish town, too. I know it's hard. I just no longer care.
