The 29-year-old completed her hat-trick before the half-time whistle blew before adding a fourth in the second period, while Fran Kirby, Lauren James and Guro Reiten also made the net ripple in a night to forget for the Irons.
Overwhelmingly favourites to get the job done on the night, Emma Hayes's side took all of four minutes to draw first blood in the contest, and it was no surprise to see Kerr in on the action early doors.
Reiten sent in a free kick from the left to the back post, and with West Ham's marking leaving a lot to be desired, Kerr had the simple job of poking home.
West Ham's response to Chelsea's opener was a positive one, but any hopes of Paul Konchesky's side launching a comeback slimmed further with 11 minutes on the clock.
Kerr and James combined well inside their own half for the latter to play a slide-rule pass through to Kirby, who curled home into the bottom corner with aplomb.
The West Ham fans were not giving up the ghost despite their side's precarious position, but if the writing was not already on the wall for the hosts, it certainly was in the 22nd minute.
Erin Cuthbert was quick to rob Emma Snerle of the ball and play in Kerr, who took a touch before unleashing a 20-yard rocket into the top corner for Chelsea's third.
The first half was not all sunshine and rainbows for Chelsea, who lost goalscorer Kirby to injury just before the break, but Kerr would complete her hat-trick in stoppage time, stealing in on a loose backpass from Hawa Cissoko and slotting home.
How one would have loved to have been a fly on the wall during Konchesky's half-time team talk, but any cries from the former defender to rally his troops went unanswered, as Chelsea made it five after 55 minutes.
Sophie Ingle's drilled pass found James on the left, and the 21-year-old cut inside before firing home, and it was six for Blues just five minutes later, with Eve Perisset crossing for an unmarked Kerr to head home her fourth of the game.
The Blues were in a merciless mood all evening long and had no plans to stop at six, as in the 65th minute of the contest, Reiten's effort inside the area took a significant deflection before nestling into the back of the net.
Chelsea threatened to add to their tally in the dying embers, but West Ham kept the Blues at bay in the final 25 minutes to avoid an even worse scoreline, and Hayes's team now prepare to meet Arsenal in the final at Selhurst Park on March 5.