"I'll start usually maybe about five o'clock at night and play until two, three o'clock in the morning," says St. Hilaire.
At age 69, St. Hilaire has found time to play hundreds of video games even though she has 12 grandchildren and finds nothing atypical about the hobby.
"To me I see nothing unusual about it," she says. "I guess it's because I've been doing it so long."
CBS News correspondent Richard Schlesinger reports she's not really that unusual. The video game industry surveyed players and found almost 20 percent of them are 50 years old or older.
"You're supposed to be a grandmother, you're supposed to be waiting to die, sitting there knitting or something," says St. Hilaire, but adds, that's just not her.
She got interested in video games during her frequent visits to nearby bowling alleys where she discovered the arcade games off to the side. She jokingly says she gets her aggression out by shooting people.
"Oh yes, it's fun," St. Hilaire says.
Nowadays she can shoot anything she wants in the privacy of her own home. We saw her shooting a round of golf with her oldest grandson Timothy who regularly challenges her.
"She definitely showed me the way of gaming," Timothy says.
This time, Timothy won. It happens — but very rarely.
"If you saw her in a store, she'd be polite, respectful," Timothy says. "If you put her front of a videogame, she's going to kill whatever's in front of her."
And Barbara St. Hilaire is a star of sorts with much younger players — her grandchildren's peers. She has attracted attention at MTV, which is featuring her on one of its Web programs.
Here she uses her professional name — "Old Grandma Hardcore." And she was just hired to review video games for the MTV generation.
"I thought she was cool, I thought she was awesome," says Alex Porter, a senior MTV.com editor. "I mean, she's the dream grandma. Who wouldn't want your grandma to be playing games with them?"
And she probably knows more about video games than a lot of the MTV kids. It's sort of like an old dog teaching new tricks.
MTV, like CBSNews.com, is owned by Viacom.