People always go overboard with lawsuits. One teacher does something wrong and the whole school or district gets sued because that's where the money is. Individuals are responsible for their own actions. Stop trying to get rich off your dead fiancé.
I'd say that since the customer called Comcast for service (rather than the customer calling the contracting company), and the fact that the contractor that showed up to perform the work was representing Comcast, Comcast would be the proper party to sue. Comcast, in turn, would then sue the contracting firm.
