Normal
I am obviously not the one picking up the pieces when she is done, but I would encourage her in her what you call "illogical" factor. Some of the greatest performers in music (thinking of Will i am of the Black eyed peas just to name one) have real anxious, shy personnalities. The stage can feel like a buble and you don't realize what you have done until it is over (personal experience). And I COMPLETELY understand not wanting the afterward attention (still personal experience). Really nothing wrong with that. It might look "impolite" to some people, oh well... the "fans" will survive. As long as you don't force her and she understands the consequences, let her do it and embrasse it. Did you ask her why she does it?