"I was stunned. That would be the word. I mean, we've never had a contestant come in at 105 lbs.," Harper says in an interview airing next Thursday on the Rachael Ray Show.
Frederickson, 24, started the show at 260 lbs. When she left as a finalist three months ago to work on losing weight at home, she weighed 150 lbs., and later lost 45 more.
"What people don't understand is, when the contestants leave to go home … they're in charge of themselves," says Harper, 48. "So, I had not seen her until that night, and so when she walked out, I was just kind of like, whoa. And I’ve been on the show since the beginning, forever."
Frederickson worked on the show with trainer Dolvett Quince, who wrote in a Facebook message Wednesday: "Please try not to look at one slice of Rachel's journey and come to broad conclusions. Rachel's health is and always has been my main concern and her journey to good health has not yet ended!"
Harper and fellow trainer Jillian Michaels, who did not work with Frederickson, released a joint statement Wednesday on Twitter distancing themselves from the contestant.
"We're not comfortable commenting on Rachel's journey because we weren't her trainers and weren't given an opportunity to work with her at any point," they wrote. "Any questions about the contestants on The Biggest Loser should be directed to the show's producers."
For her part, Frederickson is happy with her new body, saying on Tuesday's finale: "I just love myself, and I am embracing it." On a conference call Wednesday, she added that she exercises three or four times a day, and that her "goals are to be healthy and strong."