Hawke's Bay prevailed 46-31 against Northland in the other semifinal and will travel south this weekend.
Otago had too much pace out wide for Tasman and scored five first-half tries to lead 35-0.
First five-eighth Rosie Kelly had a tremendous match. She skipped in for two tries and drilled seven conversions in a 24-point haul.
The midfield pairing of Teilah Ferguson and Amy Du Plessis got a lot of traction and openside flanker Morgan Henderson put in a good shift.
But Kelly was the star. Her attacking instincts put her side on the front foot and she will be a threat in the final if she maintains her form.