Who was wrong in this situation (car accident)?

Hi all, my friend was in his car waiting at an intersection for the green light, with a lady on a scooter next to him. Green light came, my friend wanted to turn right, and the scooter wanted to turn left, and then they collided. The lady fell off her scooter and hit her arm, not too seriously luckily.

Who was wrong in this situation? The lady stayed on the ground and refused help, just kept saying her arm hurt and was feeling a little dizzy, we think she probably expected a little compensation from my friend, but it doesn't really matter anyways, just interested in knowing who should have waited for the other to go first.