This may not be a popular statement, but...
I am really hoping that it WAS her choice to go with him, and she wasn't forced, for a couple reasons.... mostly being that I believe it puts her in a much safer place for now. If he does think he's in love with her, and cares about her etc.... there is a much better chance that he will NOT hurt her and WILL let her go when they are finally caught. Or she can decide she needs to go home and he will let her. If he took her against her will, its much more of a fight to get her back, and if he's as some are making him out to be, which may well be true... he has NOTHING to lose. We do NOT want it to come to that. So i'm going to choose to look at it as she wanted a 'vacation' with him, and had every intention of coming home on HER terms....(thus the being grounded when she did) and now its blown up so much more than they thought, she is scared. It needs to be put out there that she will NOT get in trouble if she comes home.... and if she does think she is in love with him (as many many many teenagers 'think' at the time) that he can be helped and will not be hurt etc. Lets figure out a way for a peaceful homecoming.