To be honest I think most providers work a 10 hour day unless we have families all working close to home. Personally I wouldnt have a big issue with it. If you put it in your newsletter about the 9 hour day as a reminder you might get her to thinking about it and she may look for care elsewhere assuming that your hours are non negotiable. Do you want to lose them for the sake of an extra half hour or even hour a day? Just re read your post and this may only be an issue for a couple of months. I thikg I would just do since she's been there for 2 years. I'm sure you wouldnt want things to end badly at this point.