The marriage announcement of son Frederick George, in 1920, puts Caroline at 4 Clarendon Street. I couldn't find any possible matches at that address though in 1921.
Dover Express
18 Jun 1920
age 1
Marriages
Matcham-Litchfield
- On June 12th, 1920,
- at St James's Church, Dover,
- Frederick George Matcham,
- youngest son of Mrs Matcham
- and the late Mr Matcham,
- of 4 Clarendon St., Dover,
- to Ruby Margaret Litchfield,
- only daughter to Mr and Mrs Litchfield,
- of 3 Trevanion Place, Dover
As an aside, in case you haven't seen them, there's quite a few newspaper items for the family, including for Caroline's death, husband Stephen's death, son William Henry's death (1940) and various items.