Because in my own opinion Avril is not really shy and introverted, She is only shy towards her fans.
Why do i think she is not shy and introverted? She goes to parties and go clubbing, befriending, dancing, drinking, talking with total strangers. Those are the stuff shy people will not do.
Take note, i said total strangers, if she can talk , hang out with total strangers in the club, why can't she take the same warm and openness to us fans? Or maybe she doesn't like us at all ( unless that fan warmed up to her )
But what about your opinion guys?