I'm puzzled that Grand Circle would pursue your roommate for an extra grand. It would be one thing if she were part of a group that booked the trip together. But she appears to be an innocent bystander. Raising the cost of her vacation makes no sense.
Grand Circle's policy is this: If a scheduled passenger can't make the trip, and a traveling passenger is either unable or unwilling to share accommodations with another single traveler, that passenger is asked to pay a single supplement fee. Why? Because the hotels charge Grand Circle for the loss of the second traveler.
Then there's the whole issue of the TripMate insurance and the way in which it was promoted. You must read the fine print. The brochure may say, ''Cancel for any reason,'' but the actual terms of the contract may say something else.