I cannot identify her in either the 1841 or 1851 censuses, so do not know her birth or age.  Her death certificate, for a tenner, would probably give her age at death.
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Her death:

Surname First name(s) Age District Vol Page
Deaths Mar 1856   (>99%)
Powys Harriett Ashby 7a 49
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This looks, from the date to have been her child:

The Leicester Journal on the 15th Sept 1854 had this notice, on page 3, of a birth:

“On the 8th inst, at Ashby-de-la-Zouche, the wife of the Rev Spencer Percival [sic] Powys, of a daughter still-born.”
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Their marriage notice from the Spectator:

“On the 21st, at the British Embassy, Brussels, the Rev Spencer Perceval Powys, youngest son of the late Hon. and Rev. Frederick Powys, Rector of Achurch and Aldwinkle Northamptonshire, to Harriet, elder daughter of William Hole, esq., of London.”
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