Doctors are convinced it wasn't conventional medicine that saved the life of 3-year-old Lily Slater, but rather the love of her twin sister, Willow, London’s Daily Mail reported Sunday.

“Willow was the best medicine that Lily could ever have asked for,” said the twins’ mother, Shirley Lydon, 38, of Boldon Colliery, England.

After battling a brain tumor, Lily’s cancer is in full remission – and doctors are convinced it was Willow’s sisterly love that healed her.

At first, surgeons removed most of the tumor and Lily underwent chemotherapy and radiation, but the young girl's depression made treatment difficult, Lydon told the newspaper.

Doctors actually encouraged Lily’s parents to bring Willow to the hospital and Lily’s spirits lifted immediately, especially when Willow insisted her hair be cut short to match that of Lily’s.

“As soon as Willow arrived, she was back to her bubbly self,” Lydon said of Lily. “It was amazing to see.”

Click here to read the full story from the Daily Mail and to see a picture of Willow and Lily.