A Christmas Superromance by Pamela Bauer! She's the author of "Seventh Heaven".
Teh back cover says: "Was the reward worth the risk? Julliet Osborne was steeped in family tradition and old-fashined values. Then she met Ross Stafford, a jazz musician, sometime actor and teaching assistant, and he turned her world upside down. He was a man who wanted no ties, who went where the wind blew. Moreover, he was the object of her younger sister's affection.
Could Juliet allow herself to become involved with such a man? How would it affect her relationship with her sister? Worse, how would it affect the custody dispute initiated by her ex-husband?
There were two things juliet wasn't willing to sacrifice: her daughters and her integrity."