Lassila, the defending gold medallist from Vancouver, said she executed the jump on Tuesday and was excited to become the first woman to do it.
"I'm the first woman to do a quad-twisting triple somersault, which is massive," the Australian skier told Fairfax.
"I've left my mark on the sport forever. Whether or not I do it in the competition, I've done it. I don't really care what anyone says: it's a massive feat.
"Everyone, the whole tour and coaches, were really happy for me, which is cool. It's a major achievement in my life. It's a trick the guys do week in, week out. It's massive. Another box ticked."
On an increasingly soft course at Rosa Khutor's Extreme Park, there's still a question about whether she'll use it any stage in competition.
But it may be a game changer should she progress all the way through to the four-woman final.
The technical difficulty of the trick would exceed anything another woman could do.
Meanwhile, Lassila has criticised the Ten Network for concentrating on crashes in training rather than excellence in her sport.
"That's the unfortunate thing," she said.
"They captured vision of me crashing the other day, but they missed vision of me making history the next day. I actually did it. That's more newsworthy for me."