Scotland Yard confirmed they detained Mona Thwany, the wife of Taymour Abdelwahab, on Tuesday in the southern English city of Luton.
"At 6:15am Tuesday morning, counter-terrorism officers raided a residential address in Luton, Bedfordshire," a Metropolitan Police spokesman said yesterday.
"A 28-year-old woman was arrested on suspicion of the preparation of terrorist acts. She has been bailed until mid-November."
Abdelwahab, a 29-year-old whose family fled from Iraq to Sweden in 1991, blew up himself and his car in an empty side-street off of Stockholm's busiest pedestrian thoroughfare, injuring two people.
Police believe the bomb may have gone off prematurely, shortly after Abdelwahab got out of the car strapped with three other devices.
Before the botched December 11 mission, Abdelwahab had lived with his wife and three children in Luton, north of London, where he had graduated with a degree in sports therapy seven years earlier.
Shortly after the attack, beauty stylist wife Thwany said she was "devastated" and had no idea what her husband had planned.
At the time, Swedish officials said they believed Abdelwahab hatched the plan alone, but had support from others