What Can I do?

I've got a problem; someone I know went missing the other day, and she mailed me some of her stuff (a Minato plush, a plush lion handpuppet, and a few books with some of her art and writing in them). I don't think she'd be stupid enough to run away, but it really seems like she has. She has problems, and I don't blame her for running away if she did, but I'm scared that something bad might happen to her. She's not very 'Street Smart', and I wonder if she'll be okay.
What can I do? I'm really worried about her, and I don't know how to cope. She's my best friend, and I don't think she'll survive on her own. No one probably cares, but I'd really like some advice on what to do, because we're both only 13, and I want to be able to help her, or get her back here, or something, before something bad happens, but she doesn't have her phone, or anything...

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