The 32-year-old had developed a close friendship with the 'Back to Black' star and was photographed outside her Camden home on Saturday, after news of Winehouse's death broke.
Speaking to ITV1's This Morning, Horgan-Wallace hit back at suggestions she had played a role in her friend's death by encouraging her partying ways.
"I'm heartbroken anyway, losing Amy. I just want her back," she said. "But to have this thrown at me, and all the internet hate that I'm getting now. The messages have been just vile and it's hard because it's not true. There's not a scrap of truth in it."
Defending herself against the accusations, she explained: "A certain journalist said that I was seen with her... he also said that I need to ask myself what I was thinking being in that situation with Amy when she was perhaps quite fragile.
Horgan-Wallace said that it had been two months since she had seen the 27-year-old, who she met through a mutual friend. She told presenters Eamonn Holmes and Ruth Langsford that the singer had beaten her addictions.
"She got herself completely well and she did the impossible, which was to get clean," she said. "I'm just so proud of her for getting past it and overcoming it. She did the impossible as I say and she really did."
> Amy Winehouse mourned in Camden
> Amy Winehouse to be celebrated in ITV2 documentary
Watch the video for Amy Winehouse's 'Tears Dry On Their Own' below: