[ronebee]

did you put in claims and get declination letters from your daughters carrier and the boyfriends carrier? I am a New York Insurance Broker/Agent and I know the laws are different in Mass, and it appears that the rental car company was either self insured or that their insurance carrier is attempting to get money for the other vehicle.
I don't know, but it would appear to me that the rental company accepts a great deal of third party risk just by the fact of the business that they are in. They are in the business of renting cars for profits, they have to accept some (or maybe even all) of the risk that would come from one of there customers doing bodily injury or property damage to a third party. My teo cents worth.