[X] Get her name (along with the names of a bunch of other kids) by pretending this is a normal mayor thing. Then approach her at home later, and talk to her and her parents together about everything. And bring Giles.
[x] Separate her out from the crowd and tell her everything. She's sort of young for active duty, but she definitely needs to at least find out what's going on, meet the relevant people, and get a radio.
[X] She's at least two years younger than Buffy was when she was called, and that's too young to be thrust into everything Hellmouthy with the situation as dangerous as it is right now. Buffy won't tell her what she is (yet), and she won't tell anyone else about her either.