Step on the marker outside your apartment to start this mission. (This becomes available after finishing the blue cop mission Popstar Lead 2) Get your motorcycle and drive her to the Bam Bam Club, the temple and the martial arts school.
During this sequence, you'll be in a short training class with Sifu. Follow the instructions then finally defeat all students. You'll get Amanda's phone number, learn the Sweep Kick Knockdown and Workout Clothes afterward.
Sifu will also teach you new moves by for each of his Jade statues that you recover.