Sesselmann, who struggled throughout the soccer tournament, tripped and fell during a crucial moment of Canada's quarter-final match against England at BC Place.
That mistake led to the first England goal from Jodie Taylor, in a game that ended Canada's dream to win the Women's World Cup on home soil.
Following the 2-1 loss, Sesselmann rushed by the media, with tears in her eyes, declining requests to answer questions about the match.
A message she posted on Instagram at about midnight Sunday answers many of those questions.
"Words cannot describe how utterly heartbroken I am. The tears have not stopped flowing and this one is going to hurt for a really really long time,"she wrote.
"Yes I slipped, yes they scored and yes you can blame me all you want ... if that's what makes you feel better fine."
Defender worked hard to recover after injury
The 31-year old, who has played 40 matches for Canada in her career, suffered a serious knee injury in the buildup to the World Cup, and had to convince coach John Herdman to keep her in during their first match against China.
"No one knows how hard I worked to get back from injury to be a part of this special team and make a difference," Sesselmann wrote Monday.
"I know my worth and I know all the great things I've done to help this team get here."
Then she fired back at her toughest critics, many of whom sent messages directly to Sesselmann on social media.
"For all you classless people with your negative comments and threats you know absolutely nothing. You can sit there and choose to focus on every negative and pick apart our team BUT you have NO IDEA how much passion, heart and hard work this team puts in."
The loss killed Canada's hopes of becoming just the second team to win a Women's World Cup on home soil.
England will play Japan on Wednesday in Edmonton. The U.S. takes on Germany on Tuesday in Montreal. The winners will play at BC Place on Sunday for the World Cup title.