She is in the 1861 census [1] living in Brunswick Street.
Census
1861
Joseph Richardson Head M 25 Lambeth, Surrey
Matilda Richardson Wife F 20 Kensington, Surrey
Mary Ann Richardson Daughter F 2 Lambeth, Surrey
Elizabeth Richardson Daughter F 0 ..., Surrey
Sources
↑ "England and Wales Census, 1861," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:Q2ML-RBWN : 10 December 2017), Mary Ann Richardson in household of Joseph Richardson, Christchurch, London, Surrey, England; from "1861 England, Scotland and Wales census," database and images, findmypast (http://www.findmypast.com : n.d.); citing PRO RG 9, The National Archives, Kew, Surrey.
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DNA Connections
It may be possible to confirm family relationships with Mary by comparing test results with other carriers of her ancestors' mitochondrial DNA.
However, there are no known mtDNA test-takers in her direct maternal line.
It is likely that these autosomal DNA test-takers will share some percentage of DNA with Mary: