Erm, a hell of a lot of people seem to be giving strange responses here, why are you asking why she didn't just stop? she wasn't the one at fault, would you ask a shooting victim why they didn't move out of the way where somebody was firing a gun?
The cab driver tried to change lane into one with a car in it meaning he either didn't bother to check his mirror or didn't care (either driving without due care or attention or dangerous driving).
You have two witnesses (although no independent one) which will give you an advantage in court if it goes there. Your correct to contact the police over this after all what would have happened if he had forced her up the kerb and she had hit somebody?
His claim of not hitting somebody so not having to give details is rubbish, if you pull out at a junction and force an oncoming car to swerve into a wall that's your fault, this is no different