FreeBMD has the deaths of two Mary Twysdens, on in Q2 of 1839, Marylebone, v.1, p. 187 and the other in Q1 of 1879, aged 86, E. Stonehouse dist, v. 5b. p. 233.  The age of the latter makes her seem highly likely to be her, dying 7 years after he husband, so I have entered this up (subject to correction later!); however her husband also has his death registered at E Stonehouse so that clinches it, in my mind.  It is possible that the first Mary was the elder dau. of the bishop of Raphoe, or a wife of some male Twysden.

Their marriage licence abstract:

First name(s)          HENRY D
Last name              TWYSDEN
Licence year           1819
Licence date           20 Jul 1819
New calender date      20 Jul 1819
Bride's first name(s)  Mary
Bride's last name      TWYSDEN
Groom's first name(s)  Henry D
Groom's last name      TWYSDEN
Place                  Dioceses of England & Wales
Record set             Faculty Office Marriage Licences
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Their marriage abstract:

First name(s)           Henry Duncan
Last name               Twysden
Spouse's first name(s)  Mary
Spouse's last name      Twysden
Marriage year           1819
Marriage date           22 Jul 1819
Marriage place          Richmond
By licence or banns     By Licence
Groom's first name(s)   Henry Duncan
Groom's last name       Twysden
Groom's place / parish  Devon - Dartmouth
Bride's first name(s)   Mary
Bride's last name       Twysden
Bride's place / parish  Of this parish
County                  Surrey
Country                 England
Source                  Parish Register Transcripts
Record set              Surrey Marriages
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