How do you know if a girl likes you?

[Gt]

In January I met my friend's sister (through Facebook). Ever since we've been talking sporadically on and off. I haven't met her personally, but I'd really like to. Usually the conversations last about seven days and they just stop and she doesn't respond. I find it weird, and it's killing me to find out why she isn't responding. Is there any way to figure out if she likes me, as a friend or more? I'm really desperate. Thanks.

[Asa]

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[Kallista]

OK. Im a girl myself so I might as well know.
Does she answer other ppl's wall and not urs.
She can just be busy.
And maybe if your message is way too long, I dont think she'd even be bothered to reply. If its boring...nope, she wont reply.
Or maybe she thinks youre a little desperate, or that she shouldnt really talk to 'strangers' on fb. Unless get ur friend to bring you to his/her house for some project or just some excuse.
Btw, your replies should be funnier and such, like entertaining. Flirt a little, dont play safe, cos you never really want to become a really good friend with someone you really like.