Should I be worried that she didn't message me back?

[James]

I did some little flirting with her on facebook for like a week (I liked her new profile picture, we had a poke war, commenting random google images on her wall for like an hour lol, etc) and then Monday she poked me, and I poked her back, but now she hasn't poked me again since the (she's usually almost never on during the school week though, last week was weird). I wanted to ask her to hang out this weekend sometime, so then two days ago (Thursday) I saw her on and I said "hey loser" to her on chat, but she didn't reply and it turns out she didn't even see it until last night (Friday). Should I worry that she didn't message me back? I mean I wouldn't message someone back a day late if they just said "hey," so I don't think so. And should I try messaging her again tonight or should I wait a day or two longer?
Thanks
PS I know that just because I flirted a bit with her doesn't make her mine for the taking, but it just seemed weird that she abruptly stopped all contact. And I know that this should be a pretty insignificant thing to worry about, but I just really like her, I guess.

Oh yeah and a few weeks ago something similar happened where I sent her something and she didn't reply and then that time she replied 5 days later. Although that actually had something to say, it wasn't just "hey" (I sent her a picture of a turtle and told her it looked like her...she seemed to think it was really funny). That was the first time I really flirted with her and I was encouraged by her response then and afterwards. I just feel like I've messed something up. I'm not exactly experienced with this kind of thing.

[Christina]

ok i cant be bothered reading this. but relax a bit i am sure she have many other things to do.. maybe shes in the toilet or she had a problem with a family or friend member.. jsut wait a bit

[KT]

some girls just get anoyed or bored with poking so just let it go everything is prob fine

[Melody]

I'd give it some time, you don't want to overwhelm her. Maybe try sending another hey or hey haven't talked to you in a while just wanted to say hi and make sure everything was okay. If she doesn't reply then, then I would take that as a she's not interested anymore or maybe something came up in her life and she's not looking for a guy right now but doesn't want to hurt you. But def don't stress about it, it'll turn out the way it's suppose to in the end.