It's all part of an effort by her family to celebrate the 107th birthday of the woman everybody calls "Gramma Rose."
Her great-granddaughter, Alexis Daiter, put a post on Reddit last month, asking for people to send in a card to the woman who was born before both world wars.
As Daiter wrote in the post, her great-grandmother has always loved to read and re-read the cards that she gets.
More than 300 cards ended up coming in, from as far away as Mexico and South Korea.
Daiter told CBC News that every time she checked the mailbox, it was stuffed with more well-wishes from the people who heard about her great-grandmother.
"It's amazing," she said.
For her part, Lefko-Cohen says she has a family that is at the root of her vitality.
"Why I'm the way I am and where I am is for the family I've got," she told CBC News.
Click on the video to see a full report from the CBC's Kate Adach.