I would like to pick up again where we left off last evening. Thank you for the additional information on why your daughter ran away and her wanting $150 for the prom.
This is a difficult situation. On the one hand she has broken your trust by running away and by using drugs. Secondly, there is the issue of the prom and she is a senior (correct) so this would be her last prom - a very big deal for girls.
But...you do not want to reward her poor choices (running away and drug use) by giving her $150 and acting as if nothing has happened. No that would be a very poor choice.
I advise that you sit down with her and lay it on the table. That is to say, "Honey, we need to have a talk about your running away, your drug use, and prom. I know this will be difficult for all of us, but if you want to go to prom we are going to have to talk this out."
Next, I would ask her what consequences there should be for running away and using drugs. Now...this is the interesting part of parenting. Do not tell her what you think those consequences should be. Kids most often think of far worse things than parents do. That's because they know they have broken the rules and, because this was a big no-no, they believe you are really going to be especially hard. What most often happens is the kid says...I don't know...what do you think Mom/Dad. What you say is, "We need time to think about that. This was real serious." Then .... you don't answer. You can go on to talk about why she wants to go to the prom and ask her what ideas she has for raising the money on her own.
End of discussion for today. Your job now is to let her think about what those consequences should be and how she can raise the money for prom.
She is going to ask you several times what are my consequences. Your answer is, "We are still trying to decide." Give her a day or two of wondering.
Then...ask her again...what consequences do you think are appropriate. She is likely to come up with a very harsh punishment for herself - probably far worse then what you would decided. Think about what she is offering and see if you feel it is appropriate.
With this method...the child has to really think about what they did, they have to worry about the consequences instead of you worrying, and in the end the consequences are going to make a difference in how they behave next time around.
You can read more about this method at: www.loveandlogic.com
This parenting method puts the parents in charge and makes sure that the kid is not running the house!
As to the prom...one suggestion would be that you borrow the money to her and she pays you back through chores or by getting a job. Or work out a deal that she has to raise so much on her own and then you will match that amount. I would not just hand over the money without her making significant effort to pay part of the cost.
I wish you the best!
Please know that I am here to continue our chat, just address your response to me - Dr. Levang.