Megan and Melody have been wanting to get spitted for a while, and they might not want to share the roasting pit spotlight with Laura. Nothing against her, but they'd like to stand out and so might Laura, right?

Perhaps Laura might be interested in chain-cooking, instead? Have her swallow a weight on a long, strong line, use the line to pull a metal chain through, pull the chain taut, and tie it to her ankles. Suspend her by the chain coming out of her mouth, and roast her vertically. That lets the two sisters and Laura each stand out separately, and lets each put on a different kind of show. (And someone might enjoy fucking Laura while she's suspended, before she's over the heat.)