The glamour model admitted to making herself sick in the house due to "the stress" of their infamous 'pantsgate' argument, but later assured fans that her bulimia was not back.
Recalling the fight to Now, McLean said: "I love Denise and admire her on Loose Women but it really got to me that she seemed to think because we've posed in magazines we wouldn't mind showing our bodies in the house.
"My eating disorder's been well documented in the past but, although I thought I'd beaten it, I actually made myself sick in the house that night.
"I felt so desperately upset - it was my only way of coping. The rest of the housemates thought I was just crying in the toilet."
After the story was published, McLean took to Twitter to clarify that she only went "back to old habits" that one night and had been healthy since she left the house.
"My eating disorder is not back," she wrote. "I'm fine I was sick once in the bb house as anyone with an eating disorder knows there's certain triggers.
"And the stress of the house plus What Denise had said about me which wasn't shown! Made me go back to old habits ONCE !! I'm fine now."
McLean finished seventh in this year's series of Celebrity Big Brother, which Welch went on to win.
> Celebrity Big Brother's Nicola McLean: 'Denise Welch clash cost me'