You can't throw a bunch of adjectives together and expect English to cough up some magic word. It might happen, but then again, it might not.
If you want to focus on her beauty, use
beautiful, attractive, appealing, charming
If you want to focus on her appearance, you could try
classy, elegant, sophisticated... or even resplendent (depending on the case)
For confidence, try
Modesty, in some senses, goes against confidence, but you can use
For understated sexuality in particular, I'm partial to
(of people or their behaviour) attractive and showing a good sense of style
or, in extreme cases
Attractive or gratifying physically, especially sexually:
PS - In my humble opinion as a reader, I like writers to describe girls with as many specific adjectives as possible, rather than be too laconic about it. Even your description in the post would mean more to a girl than any single word could.