Sisters who were just 10 feet from a bomb that ripped apart a London subway car are having flashbacks about their "horrifying" experience as they are treated for their injuries, their mother says.

Emily and Katie Benton (search) of Knoxville, Tenn., were chatting about their day as tourists in the English capital on July 7 when the explosion sprayed hot metal and fire through the subway car. A woman seated next to them was killed, their mother, Patty Benton (search), said in an interview broadcast Monday on ABC's "Good Morning America."

"All of a sudden, the lights went out on the train and they heard the noise and they thought that they were on fire. Emily thought she was literally burning to death," Patty Benton said. "The things that they've said about it are just horrifying."

Emily Benton, 20, and Kathleen "Katie" Benton, 21, were flown from London to Duke University Medical Center (search), where they were listed in good condition. Emily Benton suffered broken bones and lost skin on one foot and a fractured hand. Katie Benton suffered shrapnel wounds in a foot that exposed tendons and bones.

The bombings of three London subway trains and a bus killed 55 people, including the four bombers, and injured some 700 others.

Though the sisters are regaining their health, that has freed their minds to think back to the moments after the explosion, Patty Benton said.

"I think they have their ups and downs. They're starting to have some flashbacks and things like that, that are hard for them to deal with," she said.

Doctors said Friday the young women were expected to spend another week at Duke before going home.

Patty Benton and her husband, Dudley, said they refuse to hate the terrorists who changed their daughters' lives.

"That's some awfully distorted lies they've been told, that this somehow is doing God's work," Dudley Benton said. "It's awful to fill people with lies like that and hatred, and I certainly am not going to let my heart dwell on such things or let that kind of anger and hatred build in my heart for them."