If a person asks another person to follow them in their vehicle and the brakes fail is that person 100% responsible for the damage?

Friend A asks friend B to follow friend A in their vehicle so that that he may drive a client''s car for work related purposes. Friend B does not offer to help he but agrees to help friend A out. Shortly after friend B begins driving friend A''s car the brakes fail thus causing friend B to bump into the car in front of it and in turn the car in front of them as well. While the damage was minor most of the damage was friend A''s front bumper which was loose. However friend A felt as though friend B was 100% responsible and expected her to pay for damage to all three of the vehicles and only contributed 200 dollars toward some chipped paint. While I never contested because I was afraid I came up with 1600 dollars to pay for everything. My friend gave me a full quote for the damages and said that was it, yet oddly never repaired their car and made other investments. It was only the front bumper and 600 was the amount to fix his vehicle. Should I have waited before wiring the 1600?