Her parents - anesthesiologist Jeff and former nurse Eileen - were both avid skiers growing up, and later took up Masters racing.
Flash forward two decades, and their World Cup-winning daughter is now on the verge of potentially making history at the Pyeongchang Games.
Shiffrin, 22, is scheduled to defend her gold medal in the women's slalom on Wednesday.
"I don't feel pressure from anybody, any external pressure. So when I'm not able to excel in the last quarter of the course or keep that focus through the finish, that's when the red lights are flashing", Shiffrin said.
"She's so impressive about staying focused in the process", said Mike Day, Shiffrin's coach with the US team.
Actually, Phelps' haul is 23 golds - and 28 medals in all.
Those setbacks followed a scintillating late December/early January when she was near unbeatable.
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"I've gotten back to my roots in skiing and reminded myself I'm not here just for wins but I'm here because I love the sport", she said.
"Then after that I got exhausted, going into the Cortina series put me over the edge a little bit".
She insisted that she was now back to her old self, having touched down in South Korea nine days ago for proper acclimatisation, rest and some training.
"I would like to compete in everything", she said. "I really like the conditions".
Shiffrin has one medal so far.
Not so much physically exhausted - although that is a constant factor with the daily grind of the World Cup circuit - as she was simply mentally wiped out.
"To be here and to know I can actually excel at nearly all the events is really cool".