The 29-year-old was removed from the ITV1 reality show yesterday after producers claimed that the format had become too complicated with four judges. Brook had been filming auditions in Manchester for just three days at the time of her dismissal.
A source told The Sun that, despite the payout, Brook is "so upset" over her sacking. "Yes, she started off a bit shaky but she was getting better towards the end of the auditions. Kelly has been treated shabbily."
Britain's Got Talent returns to ITV1 in May.
> Cowell feels 'very bad' over Brook axe