I'd start with NaNoWriMo sites. I'll bet there's a separate board just for youth. - Spidra Webster

NaNo has a whole section for kids, I think they should have resources there too. Writing.com is a very open community (site is kind of confusing) but really customizable to what you want to see. - Heather

Fictionpress.com is good if she wants to post stuff and get feedback. I've worked with 13y.o.'s on there. - Jessie

there's some options listed here http://alpha.spellcaster.org/links... and here http://www.davidbarrkirtley.com/teenwri... - though I don't know how often links on that second one are updated. - ellbeecee

though from that second, http://www.teenink.com looks good, from a quick look over it - ellbeecee