Interesting. In the accounts of the Hudson ditching, as far as i know all the cabin crew were female.
As for being by herself down there... well not too sure on the A320, but on tail-heavy aircraft like the 737-800, one crew member does stay down the back (to ensure doors are not opened) but that doesn't mean there is only ever one down there. The other crewmember goes to the cabin to oversee evacuation at the overwing exits. (I know this may not be the policy at all airlines but I'd guess it would be similar at most)
Sandilands needs to do more research, Qantas don't fly the 737-800 with 4 crew on a regular basis, that's only for crew sickness in a port without flight attendants. They fly the -400 with 4, but the 800 always has 5 in normal operations. So that's 2 facts wrong in the article. Better luck next time Ben.