If her name is Kelli Young, you shouldn't have any problem calling her by name. I don't think anyone expects for you to rename her to Kelli Smith.
If you refer to her as a young teen or young girl - that's where you'll run in to rejections. Like CrazySy said, it all depends on how you use it. There are some lists that didn't want to see 'young' at all on a teen site. I used to be one of them. But now it all depends on context. I'm becoming a push-over in my old age.