I think preparing a letter for your pcp is a good idea. You wouldn't be the first, believe me. Docs are so busy anymore that most welcome the help. I would also recommend giving her an article from the medical literature about the DS - just one, overwhelming her with literature will result in her not reading any of it. If you send me a pm with your email address, I can provide a great article for you to pass on to her, and good reading for yourself as well. And if all this doesn't get her on board, at some point you will need a new pcp, but since you already know and like her it would be great if you can educate her and make a supporter of her. You never know, you may be helping future patients of hers as well.