Andre Norton is my go-to for women reading fantasy and sci-fi. She wrote excellent books with strong characters, wonderful stories and interesting cultures.
In the Witch World series, I especially like Year of the Unicorn, Key of the Keplian, the Crystal Gryphon series and the first 3 Witch World books.
https://en.wikipedia.org/wiki/Andre_...hy#Witch_World
Scent of Magic is also great. I would avoid The Wind in the Stone - it's not good.
If you want sci-fi with dragons geared for an under-18 audience, try Jane Yolen's Pit Dragon Chronicles:
Dragon's Blood (1982)
Heart's Blood (1984)
A Sending of Dragons (1987)
Dragon's Heart (2009)
Patricia C. Wrede writes excellent fantasy. My favorite is probably her Enchanted Forest Chronicles,
https://en.wikipedia.org/wiki/Patric...est_Chronicles
Dealing with Dragons (1990)
Searching for Dragons (1991)
Calling on Dragons (1993)
Talking to Dragons (1995)
Other than that, it's hard without knowing her. Many authors are aiming sci-fi at older readers. My take on some authors recommended earlier:
I'm not sure Anne McCaffrey is what you're looking for - she can be a bit graphic, and I think some of the Pern books feature very strange relationships. I definitely wouldn't give her books to teenagers
I don't necessarily recommend Tamora Pierce's books. They're good, but not great, and they certainly promote promiscuity. I would give them to a 15 year old after discussing fantasy vs. reality, and how contraception and relationships actually work.
Lois McMaster Bujold tackles some very serious issues, like rape, sexual politics, transfengender, attempted suicide, etc. Some of her books depict rape fairly graphically, and the aftermath of sexual assault is a major theme in Warrior's Apprentice, the first book in the Vorkosigan series. I definitely wouldn't give them to a typical 15 year-old.