Hi, I know that you posted this message a long time ago and may have discovered more about the DaSilva family but maybe I have something to offer.
I know that my paternal grandmother was a DaSilva born in Guyana. He name was Mary DaSilva and she was married to a Francis Brandon. I'm not too sure about her birthdate because I didn't personally know her, but my father was born in 1956 so that would mean she would have been born c. 1920s. I don't know her middle name and I think she most likely changed her surname upon marriage. Also, I know she was of Portuguese descent, but I'm not sure where in Portugal she was from. Hopefully that was helpful! Please email me if it was helpful cause I'm curious as well!