I too have had this problems with my daycare parents. Parents expect so much from us as daycare providers. In my contract I have a big section on potty training,here is just a little bite of it.
Children generally achieve toilet training between the ages of 2 ½ to 3 years old. If potty training is begun when your child is ready, the task is easy and quick and can often be achieved in one or two days. Some sign to look for include appropriate language skills to communicate the need to use the potty, stay dry for long periods of time, the ability to dress and undress self, and an interest in staying dry or clean. I take a very relaxed attitude towards potty training. Please realize this should be your child’s accomplishment and not yours or mine. Children should not be compared to how others are doing. Children train easily when they are ready.
Parents must begin the toileting process at home. If successful and I’m in agreement that your child is ready, I will follow up with the toilet training here. During this time I require that children wear pull-ups for health and safety reasons in my child care setting. Please keep in mind that the activity level here can distract your child from responding to an urge to use the potty, more so than at your home. Therefore, I will continue to use pull-ups until your child can and will announce that he/she must use the bathroom(not just at home, but here, as well) and can control his/her bladder and bowels for a few minutes beyond that announcement. It will be at my discretion when you may bring your child in big girl or big boy underpants to child care.
While your child is learning to use the potty my rule is: No overalls, onesies, belts, buckles, snaps, buttons, or zippers. A second set of spare clothing is Required.
Also just a little suggestion, yes she is paying you,BUT it is your business not hers. You make the rules and they follow them. Plain and simple.
I hope this helps