andy, let me try to spell out how I imagined the evening when I first read the report...
Student Union holds a Halloween party. Prize for best horror costume.
Two smart women realise that taking the first Dracula costumes off the rail at the costume rental shop isn't going to win any prizes.
They go instead for modern horror with their WTC costumes, evidently going to some pains to make them; and they win the prize. (In all likelihood they had a drink, and they may even have had fun.)
Nobody seems to mind at the time but Murdoch's minions subsequently find out and try to cash in ("Subscribe to see the sick costumes in full!"). The women explain their thinking. People assume they're lying.
Now that seems to fit all the available facts; it's the sort of parties student unions hold, and it's the sort of costume that inventive people come up with. It's not at all inappropriate within its context (ie it's at a party, not being paraded down the high street). And it assumes they were telling the truth, which, like Gromit, I do assume.
The one thing it doesn't fit is the assumption many have made that they are immature, heartless, liars, or sociopaths. That's tabloid characterisation. (As I said, when I was a student our pursuits used to get the same treatment from the newspapers, and we just ignored it.) They sound like bright students to me.