Grace beat me to it, but I was going to point out the various entities who have professional obligations to keep things that patients/clients say to them as confidential. Honestly, it seems like an excellent idea to try out your coming out story with someone who is professionally obligated to keep it secret.
I’d say that cross dressing relates specifically to a number of health benefits (I started a post on this a day or 2 ago — the health benefits of CDing), so it seems relevant to your overall health such that it merits mentioning to the doc if you like her. In addition to being a doc, she’s also a real live human being, so it’ll be good to gauge her reaction. I say do it!