If I walk a mile in 9:51, is it in the upper 1% for a woman at 57?

Yes, walking a mile in 9:51 at 57 years old is an exceptional pace that places you in the top 1% for females in that age range, according to data from Medical News Today. 

--- Google,  AI Overview

Top 1% for my age group: WALK: TIME: 9:51 DISTANCE 1.00 AVG SPEED 6.0 MAX SPEED 8.1 IMPROVEMENT FROM PREVIOUS WALK: 23 seconds 

Part I: Warm-up exercises: Less than one minute

Part II: Speed: Increase initial speed from 3.0 to 3.8 at .01 miles at each change of speed 

Part III: Speed: Increase initial speed from 3.9 to 4.4 at .01 miles at each change of speed 

Part III: Walk: 1st mile: Initial speed: 4.4

4.5 .40 mi

4.6 .50 mi

4.9 .75 m

5.1 .85 m

5.2 .92 mi

5.4-5.5 .94 mi

5.6-5.7 .96 mi

5.8-6.3 .98 mi to end of mile

Time: 12:48 for the 1st mile

Part IV: Walk: 2nd mile: Initial speed: 5.9

6.0 .40 mi

6.1 .50 mi

6.2 .75 mi

6.3 .85 mi

6.4-7.6 .90 to end of mile

Time: 9:51 for the 2nd mile

Part VI: Warm-down exercises: Less than one minute

True Treadmill