Nina, 37, told The Sun that she has been monitoring the 11-year-old's Facebook page after a series of obscene comments were made.
She claimed: "Through Hollie's Facebook they write really disgusting messages to her. It's appalling - I don't know how they get away with it. I have replied saying, 'This is actually Hollie's mum and I'm going to report you.' I go mad at them. I did report one who was really bad."
Hollie, who broke down in tears during the semi-finals of the ITV1 talent show last year, is releasing her debut album on May 24.