They are hill people with inherited magical powers, I'm sure some ancient blasphemous ritual involving a half demon sits somewhere in the ancient past. However, Tara mentioned both a mother and a grandmother, so, as they didn't transform into monsters, no, it probably won't happen to her. "Family" was an after school special episode, I wouldn't take the world building too seriously.
The other thing to remember, this was Gen X, and was built off the experiences of people who lived in LA during the 80s and 90s. That generation was the first to live through divorce, and were just emotionally distant from their parents. You just didn't talk to your parents a lot in your twenties then, partially due to pain, but partially because they were busy raising your half siblings. It's one of the blind spots of the show.