@Memor-X was right, when Priscilla killed Teresa, Priscilla was already in an awakened state. It's true that Teresa could read the movement of her opponent because Teresa can sense the strength and speed of yoma energy flowing through her opponent's body. However, when Teresa fought Priscilla, Teresa couldn't read her movements because there was too much yoma power coming from all over Priscilla's body.
Claymore Chapter 22, Marked For Death 5, Page 26
But of course, Teresa was still able to match her. She was using just enough yoma power for her eye color to change to counter Priscilla. However, when Priscilla passed her limit, she begged for Teresa to kill her and Teresa turned back to her normal state, seeing Priscilla on her knees. At this point Teresa probably couldn't read Priscilla's movements and let her guard down for a moment leading to Priscilla being able to kill her.
In your comment, it's true that when Clare awakened and became Teresa, she could beat Priscilla. However, Teresa was that strong only because of Clare's feelings toward Teresa.
from Claymore final chapter, Last Scene, Page 7