Though the episode left her shaken, it was the kind of quick thinking she had prepared for.

Born and raised in Irvington, N.Y., Ms. Fitzpatrick was the middle child among five siblings who grew up in a cul-de-sac on a street bustling with young families. She spent much of her childhood competing with taller, stronger brothers and sisters who excelled at sports like basketball. By her own description, Ms. Fitzpatrick was “short and scrawny.” Her father, she said, still jokes that she is the “runt of the litter.”

Eventually she found her stride. She turned to running, something she continues to do today, usually at 5 a.m. (She still holds the record for the 3,000 meter run at her high school.)

A neighbor, Marty Atlas, nurtured her early interest in the markets, showing a teenage Ms. Fitzpatrick how stock tables worked. Even as a girl, her investing prowess was evident. “I remember her playing Monopoly with all these other kids, and she ended up with all the hotels,” Mr. Atlas said.

Ms. Fitzpatrick quickly zeroed in on her goal for after college: Wall Street. “It was the one place where you could succeed beyond your wildest dreams,” she recalled. After graduating from the University of Pennsylvania’s Wharton School with a bachelor of science degree in 1992, Ms. Fitzpatrick landed a job with O’Connor & Associates as part of a junior group of American Stock Exchange clerks.

She moved on to trade options for O’Connor at the Chicago Board Options Exchange. There, groups of traders gathered in pits to buy and sell major trading contracts, yelling out their orders while gesticulating madly. Ms. Fitzpatrick, once again an outsider on a testosterone-heavy trading floor, mastered the jargon and the hand signals.

It was in Chicago that Ms. Fitzpatrick learned just how cruel markets could be. In December 1994, an economic crisis was looming in Mexico that resulted in a swift and drastic devaluation of the Mexican peso. Ms. Fitzpatrick was covering a pit where so-called locals — traders who made bets with their own money — were exposed on the wrong side when the American Depository Receipts of Mexican companies moved suddenly. They lost everything.

“Basically overnight, these guys who I would stand next to from 9:30 a.m. to 4 p.m. every day lost their homes, lost their marriages, just everything in a flash,” Ms. Fitzpatrick said. “It really left an indelible mark on me.”