Why not believe in ourselves?' – Stengel spot-on as promoted Liverpool stun champions Chelsea
All three goals came from the spot, with Chelsea's Fran Kirby firing home in the third minute, before Stengel equalised in the 67th minute and netted the winner three minutes from the end on her WSL debut.
It is the first time a promoted team have defeated the reigning champions in their opening match since March 2015, when Liverpool were on the receiving end of a 2-1 loss against Sunderland.
Stengel said Liverpool came into the contest against Chelsea with strong belief.
"[We felt] we could win this game," she told Sky Sports. "It's just another team out there, another 11 players, and we've prepared all pre-season, so why not believe in ourselves?"
Speaking about her second penalty, late in the game, Stengel added: "I told myself, 'Don't miss' – please don't miss – all these people will make fun of me if I miss'. I got lucky, I guess."
This round of games was intended to be the second round of fixtures, but the first week's programme was postponed following the death of Queen Elizabeth II.
Liverpool manager Matt Beard echoed the sentiment that his team were a match for Chelsea, and that they deserved the result in the end.
"It's just the first game, and I felt over the course of the game that we deserved it," Beard said.
"It's great that we've started with three points at home – this was a fortress for us last year, and we made it uncomfortable and difficult for Chelsea today."