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.

[Loren]

Flirting on the Internet is just lame, dude. No offense, but just ask her out. The Internet puppy stuff is out dated, and while a girl will find it cute, she won't find it anything to think about in the middle of a sweaty night.

[DieFalke]

She might have taken the "hey loser" thing seriously, some girls can. Especially when they are feeling moody
But she may not have. It might b just like last time when she just took ages to reply.
Just wait and see. Time will tell

[Shadowpaws]

1. never say "hey loser" on facebook 2 someone as they can easily take it the wrong way because they don't know if ur teasing or not.
2. she may b shy. I know i am. i like this 1 guy SO much but i chicken out even when text messaging. don't assume anything like "she doesn't like me" she may like u so much its hard to breathe (let alone talk) when shes around u.
3. make the first move and show her ur interested. ive been waiting 4 a while and honestly its quite annoying when i cant do anything and he cant either. try saying "hey, i know this is awkward, but ______ and tell her what u feel. chances r she'll like it, and whats the worst that can happen?

hope this helps!