Got rear ended at left turn signal. Car in front of me stopped suddenly for U turn!

Yesterday my car was rear ended at left turn signal. Left turn arrow was green and traffic was flowing smoothly but suddenly the lady in front of me wanted to make U-turn and stopped suddenly as there were cars taking right turn on the opposite side. I was able to stop in time but Kia behind me was following me too closely and hence hit my car. Trailer hitch receiver took the impact and I did not notice any visible damage. Kia's bumper was broke near license plate. I did not call police as it was minor incident. I should have filed report based on my research afterwards. I will get my car inspected by body shop for frame damage.My question is the car in front of me supposed to stop for U-turn when arrow is green? She took U-turn and went happily without realizing what stupid act she did. via /r/cars http://ift.tt/2tcr0Tf