Vipers were 91 all out in 18.1 overs, a target West Storm raced to in 9.3 overs.
Mandhana was in ominous touch as she has been all through the tournament, having scored 48, 37 and a record equalling 52 not out in the first three games.
Her unbeaten fifty in the previous game was enough to equal the record of the fastest half-century in the competition history.
The Indian shared an unbeaten 54-run stand alongside Rachel Priest of New Zealand to fashion an emphatic win for Western Storm.
First Published: July 31, 2018, 10:36 PM IST