"It was like having a child again, instead of having a woman," her father said. "If somebody dropped a tray, she would nearly come off the bed. ...She was so frightened of men, generally, and just anything that was scary. And she had terrible days of, you know, hallucinations."
Beyond a forest of medical concerns, Piper also obsessively worried about the legal proceedings against Lynch, who authorities said had a history of violence and had paid Stefan Sylvestre to throw the acid at Piper.
"In the first few months at home, every night I'd have nightmares about my attackers," she said. "I would see them over me, I'd wake up screaming."
By day, a glance at her reflection in the mirror sparked a firestorm of anger.
"My appearance is a constant reminder of what he did to me. And almost like I belong to him, because it's not really my face -- it's the one he created through the attack," Piper said. "I think that's like the only thing I feel I belong to, is him. I always have, like, his marks all over my face, all over my body. I'll never be like the person I was born to be like -- the person I'm supposed to be."
"It was really hard," said Piper's younger sister Suzy. "One day ... you sort of thought, 'Oh, you know, maybe she's getting better.' And then it could be even just half an hour later ... she wouldn't speak or she would be really upset or she'd be angry. It was like a roller coaster."
For over a year, Piper only left her home for trips to the hospital. She dreaded going out in public, even shopping at the mall, because people stared.
Slowly, Piper began rearranging her life. "She sort of reached this conscious decision ... when she said, 'I am not going to be a victim. I'm going to be a survivor,'" David Piper said.
Eighteen months after the incident, the former self-described "party girl" decided to throw a party for those who were a part of her terrible but triumphant journey.
"I'd accepted that this was me. This was my new, beautiful face," she said. "I'd had a lot of help from the people that really mattered. I wanted to thank them in a way that I could ... and I knew it would mean a lot to those people to see me enjoying myself and out. I think that was a reward to them and to me as well."
"I never dreamed that we'd see her like that again," said Suzy. "And so to look at her I just thought that it's Kate again. She's back, you know. And it was so nice."
Her next milestone was leaving the house alone. Piper took a short walk into town. It was an emotional moment for Piper and her mother.
"I think I've got a chance to build a life, and I don't know if it's going to be that easy, but I want to try. I don't want to be a scared little child. I want to blossom into a confident, able woman," she said. "The scars, the mask, everything encased me in this little shell, and I want to break free and be my own person ... I want to be rid of that and just be Katie."
Piper first told her story in a British television documentary, "My Beautiful Face," which gave her the platform to rebuild her life. She now wants to help other burn victims receive the same extensive rehab that she did.