She could't find Edgcombe before the meeting and the painfully pragmatic part of her considered skipping.
But, in the end, common-sense won out; hiding wouldn't remove her name from the list, after all.
She tried to warn Hermione, rushed right to her.
But she was too late.
Doors blasted open and everyone scattered. She had the presence of mind to shoot Incendio at the list, before transfiguring her scarf green and running away.
Enough survived to still incriminate Dumbledore. But she'd at least managed to hide the involvment of half their members.
Score one for cunning.