You just have to prepared to look after number one in ways that don't rely on the cooperation of these lunatics.
Indeed. Mrs Obg is a great stickler for "following the rules", and in the case of an evacuation she likely would stand there and repeat "no, you go first" to everyone pushing in on her.
I had to point out to her that my approach will be different: If you are in front of me, move immediately toward the exit. If you are reaching into the overhead, I'll be pushing you out of the way as I pass beside or over you.