Kylie Jenner is full of BS by claiming she was rear-ended by a reckless driver Thursday ... because the other driver says she not only caused the crash but copped an attitude.
As we first reported ... the 17-year-old was driving her brand new Range Rover when -- according to her -- a woman swerved into her lane and rear-ended her.
But the woman's lawyer says what REALLY happened is that Kylie made an illegal U-ey with no warning and crashed into oncoming traffic.
The accident was so bad ... the lawyer -- Gary Daglian -- says his client's passenger ended up in the hospital.
And the lawyer goes on ... claiming Kylie was "aggressive" and tried to strong-arm his client into settling up for cash and NOT calling any cops or insurance companies. His client told Kylie to pound sand.