Davis never resolved her relationship (or lack thereof) with her father who was a cold and distant figure in her life. And it seems she never got over her father's abandonment of her, her mother and her sister. Davis' mother was in many ways a classic stage mother who lived much of her life through her daughter. But the mother (a photographer who helped define Bette's early image) was also a successful professional in her own right, a hard working single-mom who taught her daughters strong, Old Yankee values.
Bette Davis was a combative personality and she seemed to have a particularly difficult time with men -- studio bosses, husbands, directors, beaus. In the end she defined herself through her stardom and her body of work. Her life was her craft and her films are her shining legacy. That was wonderful for us but it didn't leave very much for Bette.
In the end, Bette's own autobiography "The Lonely Life" was aptly titled.