Can it be that she seems online on fb while she isn't? Or is she just ignoring me?

I know she has an iphone and uses the app messenger, she often appears to be online even though she doesn't see ( there's no "seen at" in the chat ) my texts and doesn't post or likes anything. Other times she gets online and answers immediately. But i don't think she's totally ignoring me, she asks me questions and then it takes her ( sometimes ) a few hours to reply. So is it possible that she just seems online on fb even though she's not?

I'm permanently logged in to fb even while I'm asleep. I also do not reply to everyone as sometimes I'm talking to one person and give that convo my attention then talk to another person when I'm done. I have a life outside fb, which takes precedence. I think you can't read anything in to the time it takes her to reply to your fb posts. Except that you may have an unhealthy relationship with facebook!