Getting a girl to talk longer/Keeping a conversation going

Long story short there is this girl I've seen staring at me in school and I tried talking to her. Here is the conversation

Me
Yo you don't really know me but I'm *****'s friend. He said he kinda knows you and I've been wanting to talk to you for a bit. Not trying to look like some 80 year old creep lol. Had I've seen you in person more often I would have actually said something. So what's up

Her
Oh hey hahah no its cool lol, nothing really you?

Me
Yea glad you understand. Hey so what grade are in? I'm guessing 11th but I'm probably wrong

Im HORRIBLE online but great in person but I never see her in person. What gets me mad is if she stares at me, shes probably attracted and if she is why wouldn't she talk to me? It's been a day and nothing, but if she wanted to talk she'd get on more often to respond.

I remember being younger on the forum and just NOT getting relationship stuff and now I'm obviously mature enough not to care about a girl. The only reason I am posting here is cause this one I like a little more and have had kinda a crush on, if it doesn't work out I'm cool w. that too.

Thanks in advance guys.