I too get migraines from scents so if someone asked me to stop or change or decrease the scents I do use in my home, I would have to tell them no as these are the scents I can tolerate.

Honestly, if a parent asked me this, I would think of them as high maintenance and not be very happy. If it bothers you this much than I think it is up to you to find another dcp as this is her home and I don't think you have the right to ask her to not wear perfume.