Dame Edna glanced at Judi Dench and Sharon Osbourne, both dressed dark, and asked what funeral they’d just been to completely straight-faced, as if she was genuinely checking in.
She didn’t wait for the laugh or a signal it was a joke. She just kept going while they were still processing it.
The insult only works because she delivers it like ordinary small talk. By the time everyone catches the implication, she’s already somewhere else.