I'm 17 as well, and I think that I might have endometriosis. My mom had it, and I seem to be developing symptoms.
Like your daughter, I have lower back pain, radiating muscle pain and when I started my period, it came every 2 weeks. I also feel the need to urinate as soon as I go to bed, even if I have just used the lavatories. My pain isn't so bad that it interferes with my lifestyle, but it's still there, and every woman is different.
I have had chronic feelings of muscle tenderness since I was 12 and I went to a chiropractor and rheumatologist. They could find nothing wrong. I'm not sure if this was related to endometriosis, but it could be.
I know for sure that I have ovarian cysts- I had an ultrasoud done when I was 13, and they were discovered. Your daughter might have cysts, as well. They are not dangerous, however, and rarely need treatment.You might want to ask your doctor for an ultrasound. If he/she doesn't think it's necessary, go to another doctor, until you find someone who will do it.
I want to mention that I don't know for sure if I have endometriosis. My suspicions are only because my symptoms are much like my mom's. I am going to see a gynaecologist in July, and the only way to determine for sure that the problem is endometriosis is by having a laparascopic surgery. This is a minimally invasive procedure, usually a day surgery, and recovery takes only a few weeks. Utrasounds can be used to diagnose endo, but usually only in very late stages.
I think that you might want to see a gynaecologist before seeing a genetics doctor. Your daughter's current doctor might have said that it wasn't endometriosis because your daughter is young. However, endometriosis is very common, even in young women. Dancing with the Stars' Julianne Hough has it ( you can look up articles online- I did, because I find it comforting to know that this is really a very common condition).Definitely ask the doctor if your daughter can get a referal to a good gynaecologist (you can look some up online to find a good one). Having a gynaecologist will be valuable for your daughter throughout her life, not just for this incidence. It is better to "get into the system" now,before she gets old enough to have serious "female problems".
In the mean time, to help deal with the pain, I recommend hot packs and light to intense exercise, if she feels up to it. Even stretching seems to help alleviate my symptoms, as does eating plenty of fruits and vegetables. It is good that your daughter is on birth control pills- my doctor told me that this is one of the non-surgical methods to treat endo, and prevent scar tissue from building up.
Overall, I think the best advice I can give is to assert yourself with the doctor. If your daughter wants an ultrasound or gynaecologist, make sure she gets one. Don't be afraid to "steer the ship" a little- it's better to be safe than sorry.
I hope this helps a little, and I hope my post wasn't too long!
Best of luck,