I have a family tree which lists a Matilda Emily Sargent born about 1860 in Birmingham.
She was indeed the granddaughter of John Sargent and Ann Sargent nee Beeny.
By 1886 she was living unmarried, with a partner and they had two boys (confirmed in a letter from John Sargent to one of his sons). In the 1891 census she is described as married and is using this partners surname. She is listed as the head of the household ‘living on her own means’ and with her two sons, next door to the now widowed John Sargent and one of her Aunt’s. Her partner/husband is not present. I do not know of his whereabouts.
I guess it is possible she was (widowed and re)married in 1893, for in the 1901 census for the same road William Jessop and Matilda E Jessop, with son Maurice, occupy two rooms at a house a few door away, from the house she occupied in 1891. So either this is the same Matilda or a very big co-incidence.
A quick search has just shown William Jessop married Matilda Emily Sargent(!) in 1893 (Wandsworth vol 1d page 852). So perhaps she was only using her previous partners surname to keep up appearances for her sons. This now does appear to be the same person. In which case her father was one Samuel George Washington Sargent and her mother Dessey Cottrill. Mattie was her familial name and her two sons from her previous relationship were Sidney and Victor.
If Tina wishes to contact me she can email me using may.croft@btinternet.com. I have several old Sargent photos, I will check and see if there is one for SGW Sargent. I definitely have pictures of John and Ann which she may wish to have.
Sorry to be so long winded, best wishes, Mike.

ps this message arrived through the Ellen Utsekanwa thread (one of Matties cousins), do you have information about her?