The 75-year-old finished the race in four hours, 22 minutes and 35 seconds.
That's faster than Borrett's time last year, when she finished second in her age group.
In an interview with CBC's Radio West prior to her departure, Borrett talked about crossing the finish line last year about eight minutes before the bombs went off.
"Everyone was totally silent," she recalled.
"Everyone was unaware of what was really happening. And then when the second bomb went off is when people really grouped together and went into rescue mode to get people out of the way so the medical services could get in."
Borrett says she decided to go back after receiving an invitation from race organizers because of her second place finish.
She says she knew Boston would be a good place to be this year, with a celebration planned, the strength she could see building within the city and the tremendous support it was offering the athletes.
Borrett says she's always been athletic, but had come to a place in her life when she wanted to socialize more and running provided the perfect opportunity.
Borrett was one of eight Kelowna runners taking part in the marathon — according to the online race tracker.