National police spokesman Wasisto, who uses one name, said Minhati Madrais was captured with her six children, four girls and two boys, in Iligan city north of Marawi yesterday.
He said bomb-making materials such as detonators were also seized.
Her husband, Omarkhayam, was one of hundreds of militants killed by Philippine forces as they battled to regain control of the city.
The Philippine government declared in late October that the five-month siege which killed more than 1,100 people was over.
Madrais, 36, is from Bekasi, a West Java town just east of Jakarta, and went to the Philippines in 2015, according to police.