I Am Looking for a Riana Whose Mother is Mari Robinson Nee Edmonds

Mari's father is Hemi Irimana which makes her my aunt. She would be from her father's first marriage before my grandfather met my Nana which the products were my dad Pakihana Hemi Irimana, a older brother than my dad and a younger sister. My dad would like to try search and find his neice Riana who he says she may live in the Hamilton area but carries her married name that he is unsure of.
Please I would love to do my part for my dad and who ever has gaps in their whakapapa, my dad is bound to fill in the missing links. He is very knowledgeable and knows his whakapapa right from the beginning.
Thank you