The Xtra Factor host, who had a much-publicised fling with the One Direction singer, relocated from her Camden flat to a more private apartment complex due to the constant presence of paparazzi outside her home.
"At my old place, the front door opened straight on to the street," she told Fabulous magazine.
"And when you walk out and you've got 20 men staring at you with cameras... it was embarrassing. I'd see my neighbours and say, 'I'm so, so sorry'.
"Eventually I decided to move east because I needed more privacy, which is what this place gives me.
"I feel much happier now. It never made me feel unsafe, it's just a real invasion of your life and everyone is entitled to a life."
Flack recently criticised a "hurtful" article written about her in a One Direction fan magazine, which showed her as a voodoo doll and advised her to "date boys your age, not your shoe size".