In the 1910 census, there is an Annie M. Smith, born abt. 1843 in England, resident in Baltimore, Maryland. I do not have access to the scanned image so I can't tell if this is the correct individual. Perhaps someone else could take a look. If she was still alive in 1910, that would narrow down the date of her death and it might be worth looking at the Maryland death index which is available on line but not easily searchable for a surname like Smith.