Sorry Anna,

I wish I had some advice for you. The only experience I have with 15 year old girls is the very faint memories of when I was that age myself .

The good thing is that your niece is not forced into coming to live with you and Mark and that she's excited about it so that's a good start. Nothing worse than forcing 15 year olds in doing what they don't want to do. I'm sure some of the others will come up with some good tips. Good luck!