Sources connected to Mel tell TMZ about the time Mel moved out of the family home earlier this year. Simon has seen plenty of Belafonte over the years, from 'X Factor' to 'AGT.'
We're told Simon and others felt something was seriously wrong but Mel B would never own up ... she would make excuses for various injuries and no one was sure what was real.
Simon stepped up and told her Belafonte was "a bad guy" and "bad news" and gave her the confidence to leave him.
The big thing for Mel B ... she has left him before, but she came back ... until now, and we're told she gives some of the credit to Simon.