Clues:
only New Zealand woman with this particular reason for fame
she lived in the 19th century
criminal matters were involved
More shocking than stealing
It *did* involve killing (but not eating!), but not of her husband.
No, it wasn't anyone related to her. And no gang was involved, just Minnie.
Clue, for what it's worth: she was a farmer. A rather specialised sort of farmer.
This was a murder case, with some interesting (and tragic) details.
It's what happened afterwards that makes it unique.
Well, that makes it easier... not.

A murder case with a tragic, unique ending that to this day is known that Minnie was the only NZ woman this happened to.
Geesh, was it something totally weird? Like she escaped to the wilderness and some animal ate her?
**humm, I must be hungry.... that was twice that I just had to mention eating.

**