During high school, she played for the Vancouver NW Giants of the boys' BC Hockey U18 AAA league, the first girl in history to play on a British Columbian midget major boys' league, playing alongside future NHLers Sam Reinhart and Alexander Kerfoot. She finished third in scoring among her team's defenders during the 2009–10 season, despite missing fifteen games with an injury. That year, the Giants won a provincial championship, and Fratkin was named a finalist for the BC Athlete of the Year award. She would also make a handful of appearances for the Aldergrove Kodiaks in the boys' Pacific Junior Hockey League.
From 2010 to 2014, she played for the Boston University Terriers women's ice hockey, accumulating a total of 66 points across 151 NCAA games. She scored 10 points in 38 games in her rookie collegiate season, notching her first goal on the 11th of February 2011 against Northeastern University. She broke out in the 2012–13 season, almost doubling her point production up to 17 points in 37 games, and picking up points in seven of the last eight games of the year. She was named an assistant captain for the team ahead of senior year, where she would go on to score a career-best 30 points in 38 games, being named a 2013–14 New England Division I All-Star and Hockey East First-Team All-Star.
Fratkin was selected 20th overall, in the 5th round, by the Boston Blades in the 2014 CWHL Draft. After graduating from Boston University, she signed her first professional contract with the Blades. She put up eight points in 22 games in her rookie Canadian Women's Hockey League season, competing in all postseason games as the Blades captured the 2015 Clarkson Cup.

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