Thomas A Knill of St Diego was born in 1905 and is unlikely to be around. I got my copy of his "Llinks of Knill" from the Knill family of Vancouver who run Knill's Alarm Systems in that city.
I do not think that Thomas Knill's researches would help you much as his trace is only confined to a Knill family in Tawstock, a village just to the south of Barnstaple and he was unable to make any connection with Knills in Barnstaple.
My own family come from Barnstaple and Braunton just to the west but my G-G Grandfather became a coastguard in 1821 and left the area. My details therefore relate to the years before that and are thus to early for you.
I have another tree of Ilfracombe and Barnstaple Knills which does include an Elizabeth Anne Knill but the only date I have is her elder brother born 1849 at Ilfracombe so I guess she would be too old and not at Barnstaple itself.
One of my daughters is Elizabeth Ann and now lives in New Zealand!