The decision ends her hopes of defending the title she won so emphatically in Phnom Penh in 2023.
The 27-year-old suffered a three-centimetre tear in her left hamstring following a fall during a 4x100m training session at Universiti Putra Malaysia in early November.
She has been undergoing rehabilitation at the national sports institute (NSI), but follow-up assessments this week showed she would not be fit in time for the Games.
Her withdrawal was confirmed by her mother, former national 400m and 800m champion Josephine Mary.
The decision means Malaysia will now be represented by only one athlete, Chelsea Bopulas, in the women’s 400m, an event Shereen has dominated regionally and still holds the national record at 51.79s.
“It breaks my heart that I can’t be there,” Shereen said. “I wanted so badly to defend my gold, but my body isn’t ready.
“The hamstring has improved, but not enough to compete safely at this level.”
Shereen had been scheduled not only for the 400m but also the women’s 4x100m, 4x400m and mixed 4x400m relays.
It was a heavy workload she had been preparing for since returning in October from the United States to train in Kuala Lumpur under a programme set by her American coach Derrick White, with local guidance from national trainer Amir Izwan.
“This year has been a roller coaster,” Shereen added. “I’ve battled health issues, I’ve pushed through setbacks, and I truly believed I could bounce back for the SEA Games.
“I’m sad, but I know this is the right call. I’m grateful to everyone for standing by me.”
Her 2024-25 season has indeed been turbulent. She opened her campaign brightly by winning the Embry-Riddle Running Elements Classic in Florida, clocking 53.72s.
But illness struck before the Asian Championships in Gumi, where she ran a fever and faded to 54.80s in the heats.
More tests later revealed deeper health complications, forcing her to scale back her workload for several months.
“After Gumi she felt weak all the time, no matter how much she tried to recover,” Josephine said. “But she worked on it and gradually got back to training.
“This hamstring setback is unfortunate, but she will come back stronger.”
Even before the injury, defending her SEA Games gold was always going to be a stern test.
Thailand’s in-form Josephine Chinenye Onuorah leads the regional charts with multiple 52-second runs in the United States this season, while Vietnam’s Nguyen Thi Ngoc (53.12s), Thailand’s Benny Nontanam (53.15s) and Vietnam’s Le Thi Tuyet Mai (53.37s) have also been consistent.
Still, Shereen remains optimistic.
“This is just a pause,” she said. “My goal is to return fully healthy, rebuild, and get back to the form I know I’m capable of for the Asian Games and Commonwealth Games.”