I read this book in grade school in the 90's. It's a fantasy young adult book about a teenage girl. She's a ballerina and has a birthmark that signifies something. There is a male that has been watching her since she was born and has something to do with her birthmark. I remember it being a dark somewhat creep/scary book. That's all that I remember about the book. Thanks!
Could it be Amy, Number 7, first book in the replica series? It involves a girl with a birthmark who's being watched by a strange man. She is not a ballerina, but she is a gymnast. Also, according to another question that had this book as an answer, one of the clones is a Russian ballerina (I have not encountered that character, but there is a French ballerina in the second book who seems to be one of the clones). It was published in 1998, which might be a little late for you, but it's a good match overall.
Specially priced! Amy Candler is the perfect 12-year-old girl. She can do anything. She knows everything. But Amy doesn't have all the answers to the mystery of her past. All she knows is that her recurring nightmares seem so real. That her crescent-shaped birthmark wasn't there yesterday. That a strange man is taking photos of her. That her mother is acting weird. That someone is sending her anonymous warnings to keep her talents a secret. Slowly Amy is piecing together her identity, but she'd better hurry.