I wasn't familiar with Turner's Syndrome and had to look it up. I noticed that one of the websites mention the importance of estrogen replacement therapy, not only to develop breast/secondary sexual characteristics but also to maintain bone health and skeletal strength... Maybe its something you can mention to her doctor to see if estrogen supplements would be appropriate--and maybe even more successful if started at this age than if she were to start it later...
Here's the blurb I saw:
Estrogen replacement therapy has been used since the condition was described in 1938 to promote development of secondary sexual characteristics. Estrogens are crucial for maintaining good bone integrity and tissue health. Women with Turner Syndrome who do not have spontaneous puberty and who are not treated with estrogen are at high risk for osteoporosis.