What an interesting puzzle! The -etta sounds Italian, but the Griz- is so close to
Griselda (sometimes
Grizel) that I rather suspect it's a variant ... in Catholic
Ireland, Italianate names would not be surprising. Any Griseldas that she might have been (almost) named after? Or, indeed, in bad handwriting,
Griselda and Grizetta could be one and the same. Might be worth digging around a bit more. Good luck!