Given what passes for normal wear in the BaDIK universe, I have to wonder if Halloween costumes are more along the lines of Elizabethan nobles and American Gothic schoolmarms.
I'd actually rank them
1. Bella
2. Cathy
20. Heather
318. Jill
Episode 8 is going to be the end of the season, and my guess is DPC will want to end on a relatively even keel for the Steam compilation. That means Episode 7 is the chance to whack us over the head with the drama club. Since DPC just played the Maya's Dad card, the biggest stick around (no, not counting that bat!) has got to be Bella. Whatever horror lies at the heart of Isabella, I don't think there's a better way to catapult it into the daylight than to finally have the MC go all the way with her.
So that's my guess. If it does happen, though, I don't think it will end well.