Gustafson praised her team’s togetherness after securing the victory.
“It is incredible to be with this team and get this win,” she told Sky Sports.
“I have to give Essex a lot of credit, they fought hard and gave us a lot of challenges.
“I’m proud of this team. It means so much. We have great chemistry and that makes this more special.”
The Lions raced into a commanding lead, ending the first quarter 26-13 ahead. Essex were not clinical enough and were regularly punished by an efficient London attack. Gustafson hit a three-pointer as they scored 11 unanswered points.
But Essex, competing in their first final, rallied in the second quarter, with Dayzsha Rogan, who finished with a personal haul of 15 points, throwing two threes to maintain the 13-point deficit at the halfway point, with her side 48-35 down.
A first-half three-point percentage of 50% kept Essex competitive as London were wasteful with their attempts, converting just one from 11.
But with 11 turnovers and six Lions steals by half-time, the story of Essex’s game was laid bare.
Whenever there was an element of pressure on them, though, the Lions found another gear after the restart led by the 27-year-old Gustafson. They ended the third quarter leading 66-46.
Essex’s defence stayed resolute in the final quarter, but London still added another 17 points to their total, the highlight of which came when substitute Kat Snytsina threw a superb three-pointer late on.