The Standing Orders don't address this particular situation.
Rachel has the floor right now. She, at her pleasure, as a parliamentarian with parliamentary privilege, is allowed to introduce her motion. If that motion is defeated, then automatically Mr. Carrie's motion would be addressed. If it's adopted, Mr. Carrie's motion would be moot, but we still could vote on it.
I would suggest that we continue on the way we're going, with Rachel having the floor.