If this happens on a nice day when you can go to a park or somewhere else I would call the Mom at 9am and tell her where you will be for the morning and that she will have to find you because you are leaving. I have done this is in the past. I won't sit around waiting and wondering and letting our busy, fun morning be ruined by a mother who doesn't have her life in order so she can be on time. The Mom at my daycare learned to be here by 9am all the time. You have to demand respect and show your clients that your contract is a legal piece of paper that is not to be trifled with on any level.