I too have a wardrobe with door mirrors on it. Jazz has only flown into it when spooked. Usually she will fly towards it and (I assume she thinks there is another parrot heading towards her!) she will stop, hover (I didn't realise parrots could!) for a bit and then turn and continue...
I have considered turning the doors around so the mirror doesnt face out, although as she hasnt crashed into it for a while I have not done it yet.