I am sure you have made your opinions known on why she cannot participate again in anything so dangerous as this secret ride. I would talk calmly with your daughter about the values of your family and the responsibility you all have to act according to those values. Tell her you understand that her girlfriend has a need for attracting attention to herself, and that it may be very hard for her to say no to some of this girl's suggestions. Speak of your trust in your daughter and your belief in her goodness. Mention that anytime she ever needs your help to solve a problem, you will be there for her -- to help without judgment, not to blame or criticize.

I would suggest that you have a talk or two with her and this friend, together. Explain your family's rules of behavior and the limits that you set, and give the reasons behind these rules and limits. Tell them you want to see them earn your trust and that you are looking forward to an improved relationship among all of you based on mutual respect.

Do not attempt to parent this other girl. If anything, have a few conversations with her mother and share. Tell her what behaviour you expect of your daughter and hers. I recommend that you purchase, The Parent's Guide: Systematic Training for Parenting of Teens, by Dinkmeyer and McKay to give you a good foundation as regards parenting responsibly during adolescence.