Well mystery method is all about how to open groups. Thats what making it different from other methods. If your 16 you have a lot of time
The younger girls are different in many ways, they dont have so much expirience. And the popularity in schools is too important to them.
But basiclly you have to use a opener to the whole group. Something what will get them all talking.
blaa blaa blaaa blaaa blaa blaaa (you can look this all up)
To make her stay around is then easy you just have to isolate her when you feel ready for it, and when you seen that shes shown your IOI.
Just say "I want to show you something" "Can I talk to your friend for a minute, I promise you'll get her back
".