What a shame. I recommend the Sword of the LORD in these cases. Then they are required to come face-to-face with their real enemy, who is not your daughter. Their disagreement is with God Himself who has already spoken on this matter.
"This day I call heaven and earth as witnesses against you that I have set before you life and death, blessings and curses. Now choose life, so that you and your children may live..." Deut. 30:19
Ping for help.