I agree with LadyStoicIsBack
the way i see it, whether one works for a corporation or a private individual...somewhere along the line corners are cut.
In my experience, that is not acceptable when it affects the innocent parties who have not been made aware or have not been given a choice.
I feel everyone plays the system in their own way, but in THIS context - she is bang out of order and needs reporting.
Her bank balance will benefit from her fuckwittery....but where's the benefit to the children in her care? She doesn't know the dc family dynamics. i grew up with very limited opportunities for family days out, a free trip with school etc was the only time i had access to the 'bigger world'. I don't feel she has the dc best interests at heart when she's 'on duty'. THAT is NOT the kind of person i would want looking after ANYBODY'S child.
The bit that icks me the worst - she interfered in a parent & child trust - knowing full well that the dc is a disadvantage simply due to his age and perceived mental development. That's awful! Kids at that age are NOT stupid and to instigate that kind of mistrust and doubt in both the dc and the parent is just NOT ON!
If i were in your shoes i wouldn't bother contacting her. Report her to the relevant authorities and let them deal with it. The only response i would send her is "i know you didn't take ds to the zoo. please refund my payment."
Don't reply to any response other than one which gives you the refund. Any refusals and further game playing - keep it as evidence.
Neither you or any other parent who entrusts the welfare of their child to another should be treated this way.