How to know if my friend on FaceBook dislikes me?

I like to think I'm quite good friends with her, but she's pretty much constantly on "be right back" when we're talking, her replies are almost always at least three minutes slow, and today she said she was "doing German homework, brb in about an hour, see you~". She's now been away for about five hours and is offline on deviantART and FaceBook, but when I logged into Yahoo Chat she was online. I sat on there for about fifteen minutes, saying nothing, then she suddenly signed out. Also, an hour after she sent the brb message, there were messages on her wall between her and her other friends indicating she was online and talking with them, but she did not appear online for me and did not respond to any of my posts between then and now. Do you think she dislikes me, or is just exceptionally slow at responding, or maybe gets easily sidetracked? I don't think I've done anything to alarm/irritate/hurt/insult her.