Can botox injections to the masseter muscle really give drastic results? Smaller jaw choices? (photo)

I recently noticed Olivia Munn looks so,so different now. She went from looking cute to stunning, and it really left an impression about how powerful a smaller jawline can be. However, it's unclear how she got such drastic results: was it more likely jaw reconstructive surgery? (which I hear is common in Asian countries) thank you!