i Register
In some senses, tallywoman is marked as archaic, informal. Watch for register when choosing this word.
noun
A woman who conducts the tally trade.
A woman who cohabits (with someone) outside of marriage.
It is used in Yorkshire, Lancashire, Cheshire, and, I dare say, various other counties. A tally-woman is the mistress of a married man, who is said to live tally with her.
A female counting agent.