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...that was the first time I ever got flirty with her)

[Brianne Chanelle]

You're flirting in the little leagues! You need to do more than facebook to get her attention. Alot of dudes probably message her! And don't overthink it. She probably felt like it was a late message, she gets the point. (:

[HILL]

If a guy messaged me if i liked him i would be writing back straight away even if i only got the message a day later, it seems like shes not interested sorry.

[sodadancelover]

I would try messaging her again. Maybe she just didn't have the time to reply and it was kind of a "bad timing" thing. Don't give up if you really like her, and if she's messaged you before and you've had an actual conversation with her then she obviously doesnt mind talking to you. Forget about her not answering and start fresh!

[Julia ☪]

You sound so cute to be so worried about it, clearly she sometimes gets busy and can't get on facebook! I think you should message her either tonight, tomorrow, or the day after, unless you REALLY want to hang out this weekend, I wouldn't risk having her be busy and then it might be awkward like oh..some other time then... so make it like next weekend to make sure it's enough time in advance so she has YOU in her schedule, instead of other plans. Bottom line is, The fact she isn't replying either means she's actually busy and can't be bothered to get on OR the answer you probably don't wanna hear, but I really don't think its this, -she only replies to you later because she'd rather talk to other people the moment you messaged her, and then gets bored a few days later and sees your message and says why not i'll talk to him. Only reason i'm even thinking that might be it is cause I've thought like that when I didn't reply to other guys. Good luck