Hello,
I'm a descendant of James Bonner and Anna Desse (also sometimes Desso). Judging by your flag you're in Britain but a large number of us live in northwest America. A decent number of them are Mormons and if you have questions the LDS church might have better answers than our handwritten records. The information I was told is that Anna stayed behind in West Bengal and died there in 1822. She was born in the village of Sulkeah (now Salkia, a district of Howrah) and was a local Bengali woman. I hope that helps!