It depends how fit she is, however it will should take between 11 and 15 minutes.
Every woman who runs a mile will record a time of 7 minutes and 20 seconds.
15 minutes for a mile is a brisk walk (4mph). 12 minutes for a mile is 5mph, slow jogging. 10 minutes for a mile is 6 mph, respectable for age 42. Race winners in that age category may be under 6 minutes.
If you are just starting with running, try to beat 15 minutes. You can walk part of the way. Then as you work up to running a whole mile, you'll be trying to beat 12 minutes. To meet fitness standards, you want to get under 10 minutes, but that could take half a year.
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