Harper: North Security series by Skye Warren has a lot of fans. Is a bit of a taboo because the H is her guardian and teacher
About book #1:
The world knows Samantha Brooks as the violin prodigy. She guards her secret truth—the desire she harbors for her guardian.
Liam North got custody of her six years ago. She’s all grown up now, but he still treats her like a child. No matter how much he wants her. No matter how bad he aches for one taste.