Good morning ,
Here are voter's lists for a Charolette Tandy:
Mrs Charlotte Tandy, 1949 Middlesex, Ontario Middlesex East
Mrs Charlotte Tandy 1972 London, Ontario London East
Mrs Charlotte Tandy 1957 Middlesex, Ontario Middlesex East
Mrs Charlotte Tandy 1962 Middlesex, Ontario Middlesex East
Charlotte Tandy 1958 Middlesex, Ontario Middlesex East
Mrs Charlotte- Tandy 1968 London, Ontario London East
Fredrick is listed on a number of voters' lists from 1935 in the London area as the one below:
Frederick Tandy 1935 London, Ontario London
up until the mid 1970s from what i can see. London Ontario is in the County of Middlesex, Ontario.
If Charlotte is indian as indicated in the 1921 census, she may be a status indian and from one of the reserves surrounding Sault Ste Marie or London, Ontario. If she is a status indian she will likely be registered with AADNC. She may also be a metis indian and the Metis of Ontario organization may have her registered with them. I haven't found another Charlotte yet so the one Jacquie located may be the one. You may also want to contact the First Nation Bands, such as Garden Hill First Nation or Batchewana First Nation, to see if Charlotte is listed with either of them.
Hope this helps,
JDC