Put into bat, India scored a challenging 265 for 7 in their final league match. Besides Mithali, Harmanpreet Kaur scored 60 runs while Veda Krishnamurthy made a brilliant 70 off just 45 balls.
Chasing 266 for a win, the Kiwis crashed out for just 79 runs in 25.3 overs.
The win ensured Indian eves qualify for the semi-finals for the first time since 2010.
India will take on Australia in the second semi-final on Thursday. In the first semi-final, England will take on South Africa on Tuesday. The final will be played next Sunday.