Maybe what would be a good idea then is to not tell the parents how you are handling things. Maybe the response from the mother could have been avoided by just not telling her and I honestly think this is something that doesn't need to be reported to the parents in the future. You know what the parents think and how their attitude is so just deal with it yourself, no need to report every little detail to her. Put them on a schedule and deal with it in your house alone. I think it would be far more productive to work with the girls, and much more helpful to their well being to stick with them and work through this rather than just terminate when things get a little difficult. I appreciate that the mother is completely out of line to forbid what you do in your house, there was for sure a better way she could have handled things while still getting her point across that she wasn't happy with what you were doing. At the end of the day they are her children and she has the right to her opinion on all aspects of the care you provide her children even if you don't like what she says and even if she does have an attitude problem. That being said, aside from making general enquiry into how this translates at home, I don't think its necessary at this point now you have established there are no health issues, to give the mum a play by play of your bathroom routine. Do what works for you and the girls in your house and leave the parents out of it.