What Should I Talk About With Her Of Facebook That Won’t Make Her Bored Or Make Me Creepy?

Here’s the just of it:
There’s this girl that i’ve been talking to on twitter off and on since January 19 2012 and she lives 2,300 miles away but I really really want to be friends with her. I know she isn’t a fake or some old creepy guy either because I know who she is but I don’t know her in person. I also started talking to her first.
Here’s what we’ve talked a little about already:
Favorite band/favorite songs by them
favorite movies
we’ve said the AREA where we live but NOT addresses or anything like that
hobbies
About pets
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(1)She accepted my friend request on Facebook a few days ago and I thanked her on twitter but should I have done that or did I sound too needy or obsessed?
(2)What else could we talk about that WON”T make her bored? (I don’t get girls at all please help)
(3)Should I message her on twitter like before or should I send her messages on Facebook now?
(4)What are some do’s and dont’s I should and shouldn’t talk about?
Also ALL of the messages we’ve sent back and forth were direct messages so no one else would see them, for safety.
I’m 16 and she’s 18, I DO NOT want to date her or anything. She is just a really cool person and I only want to become frineds with her.
Please Be Serious And Thanks!