Just say you're sorry but you don't want a relationship right now :> and if it's because you like someone else just tell her there's someone else you're interested in. Don't worry about it too much. :>
If you say to her that you don't love her back, (I write the rest in french, if you don't understand, use google translation) ça va forcément lui faire mal au début, mais au moins elle ne se fera pas de faux espoirs.
I would say she's way too young. She's still a child. I wouldn't worry about rejecting her it's the right thing to do. She'll get over it soon enough. :>
That's the thing with kids. To them love is more of a concept as opposed to a feeling. Don't feel bad about rejecting her it was the right thing to do.
