Firstly sorry to hear that this has happened - it must be very stressful but at least nobody was hurt.
I am no expert but is inconceivable to me that you are to blame in anyway: the Old Woman has exercised poor judgement in pulling around the Lexus, but Ford Woman is at fault for failing to keep a safe distance behind Old Woman. Even if your actions caused Old Woman to perform an emergency stop, Ford Woman should still have been able to stop with out rear-ending her (as the actress said to the bishop ...)
