Is it normal for a girl to be obsessed with a girl that's younger than her?

Okay, I have a friend that I've known for almost ten years. She's the daughter of some family friends, and we get on really well, even though she's three years younger (16).

Basically, I have a very creative mind, and I love to write/come up with stories, and she's my main character in many of them - even though I give her a different name.

There's just something about her which means I'm always drawn to her. Not in a romantic way at all, I'm just constantly wondering what she'd do in situations that I invent for story plots.

I do check her facebook page often, and I get really happy when she puts new photos up as she's really pretty, and it allows me to envision her in my stories. I'm also often hoping that I'll bump into her on the street or something. But I don't do anything else, nothing harmful.

When I do see her (which isn't really that often, or as often as I'd like) I feel really insignificant and inadequate compared to her, because she's just got this amazing fashion sense and is always really sweet and kind, and feel like an awkward idiot when in conversation with her, as sometimes I'm so happy to see her I can't stop being jumpy.

I often find my self wishing I was her best friend, and know everything about her. Even though we are friends, I don't often see her so we're close but not that close.

She doesn't know any of this at all, we are friends, and have been for years. Is my behaviour normal?