She might not have been allowed to give the middle finger, possibly for different reasons and had nothing to do with her personal choice in the matter.
You should have asked for a hug

I've seen a few photos where people get to hug Avril in the M&G photos.
I'm sorry your M&G was awkward, I'm sure she takes no offence, though. Some fans get so nervous they cry, other times they act really shy(Or really talkative and the wrong words come out) and show their nervousness.