like most of what everyone else has said here, better 'situational awareness' - without seeing the build up to it though it's hard to know what. Once the attack actually started, little if anything would have helped - even carrying a gun probably couldn't have helped. After having your head stamped on once I suspect there's little you can do. Perhaps the woman had noticed him earlier and her passive behaviour was a mistaken attempt to avoid a confrontation. Possibly better would have been to confront him outside on the street (presumably that's where they came from?) if there were other people around.