When should I call?

OK, so in about march of 2006, I wrote a girl a letter. She was/is an actress in a TV movie. she's about my age (she's 14, I'm 15). She wrote back. Then I wrote back. Then she wrote back. And so forth. We don't 'know' each other all that well at all, but I think she's nice and would like to continue our friendship in ways other than snail-mail. We occasionally e-mail, but they are short and snappy ones. So now we're on each other's facebook and I want to call her, you know? but should I? I'm not much for talking on the phone, and I don't know if it'd seem to... straightforward? I mean, she's a friend now, I guess I could say, and I don't see her as a 'star' anymore, but do you think it would be all right? Do you think she would freak out? And if I do call her, what should I talk about? We don't know each other ALL that well... HELP!