The Eagles led 33-9 early in the third term of Friday night's match, but four unanswered goals from Richmond put the visitors in front with just three minutes remaining.
At that point, it looked as though the start of the Daisy Pearce era at West Coast would end in heartbreak.
But there was one more twist to come, with Eagles speedster Abbygail Bushby powering the ball forward following a teammate's dropped mark to find a running Kellie Gibson at the top of the goalsquare with just over a minute remaining.
Gibson nailed the goal with 43 seconds left on the clock, lifting West Coast to the 6.4 (40) to 5.9 (39) win at Perth's Mineral Resources Park in front of 2166 fans.
KELLIE GIBSON WITH THE MATCH WINNING GOAL IN THE FINAL MINUTE!@coles | #AFLWEaglesTigers pic.twitter.com/XQiDYtCaRi— AFL Women's (@aflwomens) August 30, 2024
West Coast players mobbed Pearce out on the field after the win, showering her with their drinks while they sang the team song in what marked a special start to her tenure.
"I'm not sure that I'm meant to go in the song and get a Gatorade shower," Pearce said with a laugh.
"It was a nice moment, but over and above, it was nice for me to see them have (that feeling).
"I know that they haven't been able to have that kind of reward of winning as much as they would have liked."
Pearce, who was a premiership-winning star at Melbourne, said winning as a coach was slightly different to the feeling she experienced as a player.
"It's probably a bit more pride (as a coach), because it wasn't me that went out there and did it or contributed to doing it - it was them," she said.
"So you just sit back in awe of their resilience and effort. Pride is the over-riding emotion."
West Coast had won just eight games across their five completed seasons.
They are now a perfect one-from-one under Pearce.
Eagles midfielder Jess Hosking, who was delisted by Richmond at the end of last year, was crucial against her former side with two goals from 12 disposals.
Isabella Lewis (19 disposals, 340m gained), Ella Roberts (20 disposals, three clearances) and Charlotte Thomas (24 disposals, 509m gained) were also prominent for West Coast, who were missing captain Emma Swanson (groin).
For Richmond, Monique Conti (30 disposals, five clearances, 584m gained) was best afield, while Grace Egan racked up 22 possessions and six clearances.
West Coast forward Amy Franklin kicked off Friday night's match with a powerful mark and a booming 45m set shot.
Hosking added a second for West Coast to give the home crowd something else to cheer about.
It helped set up a five-goals-to-one opening half for West Coast, but Richmond dominated after the break to storm back into the contest.
Eagles' Jess Hosking celebrates one of her two goals in a storming display against her former club. (James Worsfold/AAP PHOTOS)
Emelia Yassir put Richmond ahead after catching Belinda Smith holding the ball, but West Coast had the last laugh through Gibson.
"We got this gift tonight, we walk away with the win and belief," Pearce said.
"There'll be some great lessons out of the couple of minutes when we were fighting one way or another."
