Gabboim,
I don’t know when she passed away, but I think it must have been some time ago. The Chofetz Chaim was born in 1838, so even if she was 30 years younger she was born in 1868, over 140 years ago. She escaped Europe with the Mirrer Yeshiva and is buried in Queens.
Rebbetzin Zaks lived in e”y towards the end of her life–I visited her when I was in seminary.