Is walking one mile in 10.42 for a 57-year old woman be considered in the top 1% for her age?

Yes, walking a mile in 10 minutes and 42 seconds for a 57-year-old woman is a phenomenally fast time and would place her in the top 1% or higher for her age group...

Top 1% or higher for my age group: WALK: TIME: 10.42 DISTANCE 1.00 AVG SPEED 5.8 MAX SPEED 6.9 IMPROVEMENT FROM PREVIOUS WALK: 30 seconds 

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

Part II: Speed: Increase initial speed from 3.0 to 3.6 at .01 miles at each change of speed 

Part III: Speed: Increase initial speed from 3.7 to 4.2 at .01 miles at each change of speed 

Part III: Walk: 1st mile: Initial speed: 4.2

4.2 .50 mi

4.7 .75 m

4.9 .85 m

5.0 .92 mi

5.2-5.3 .94 mi

5.4-5.5 .96 mi

5.6-5.8 .98 mi to end of mile

Time: 13:20 for the 1st mil

Part IV: Walk: 2nd mile: Initial speed: 5.4

5.7 .50 mi

5.8 .75 mi

5.9 .85 mi

6.0-6.5 .90 to end of mile

Time: 10.42 for the 2nd mile

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

True Treadmill