I don't think Mel B can be solely blamed for people being bad.. The contestants are more than welcome to question song choices given to them, as seem with Ben and OTY
And with the 'cheating' thing, Fleur's backing vocals were really loud over her voice, so i can see where Mel was coming from, i don't think she was trying to ruin anyone's chances at all, just stating an opinion, which i for one shared that particular week.