Baker-Harber, while speaking to best friend Rosie Fortescue, insisted that she would slap Mackintosh if she saw her again.
The At Your Inconvenience rapper tweeted during the E4 show: "Did I just see a horse say it'd slap Millie?
"Apologies, I'm nowhere near as dignified as the other half when it comes to these situations, I call a spade a spade, a horse a horse."
The reality TV star hit back: "I'm so offended by your eloquent manner. Sorry, do you need a dictionary for that?
"Hasn't your 'girlfriend' informed you that it's just a TV show? You should try and figure out the boundaries."
Professor Green then retorted: "Of course being of the underclass I'd need a dictionary to understand a word which does not in any way apply to you."
Baker-Harber responded curtly: "And it is not a case of background. Its 2012. Who cares. Goodnight."
Green, 28, had the final word by saying: "You have a foul mouth and you have a foul mouth. That might take you a while to work out. You can't help but continually prove what a nasty piece of work you are."