The French captain's two miracle threes kept France unbeaten atop Group B at 4-0 and Britain winless after wrenching losses to Australia, Canada and Russia that had the Olympic Basketball Arena fans roaring but deflated in the end.
Dumerc, who finished the game with 14 points, was well aware that she was not the most popular athlete in London following her sharpshooting display.
"I think it is the opposite. I think everyone hates me," the 30-year-old point guard said as a wide grin covering her face.
Britain was ahead 67-64 when Dumerc let fly an off-balance, left-handed three-point heave that swished through the net with six seconds to play and silenced a roaring home crowd.
Undaunted, the plucky British team led by tenacious captain Johannah Leedham got right back to business in the five-minute overtime. Leedham scored her team's first seven points in the extra time as Britain built a 76-72 lead.
But with the game tied 77-77 and only seconds remaining, Dumerc went to work again.
This time she stepped away from the three-point line, moved to the side and launched another guided missile through the hoop with .2 seconds left before the final buzzer.
Dumerc said this sort of rescue mission was a first for her.
"Never twice in a game," said Dumerc, who scored 14 points in the game. "But on this kind of moment you don't think. You just throw the ball. For me, we lost. We already lost.
"You don't have to think. You just have to play and this kind of moment is magic. You will ask me to do it again and I will miss."
The 24-year-old Leedham scored 29 points for Britain.
"Everybody played with their heart on their sleeve. That's the ethos of our team. That's what we do," she said.
"To compete with the teams and be so close and yet so far, it's disheartening but we've come a very, very long way and we're so close. You know we're going for that win against Brazil and that would be huge for us to get that first Olympic win."
- Sports & Recreation