The pair previously locked horns over Kay's 'secret' life outside the Big Brother house.
It started over the weekend when Kay became coy with Lewis F over her situation on the outside world.
"I'm a little bit cautious because I barely know you..." Lewis F began.
"If somebody wants to be private... I don't understand why.. like..." Kay responded.
Lewis F explained: "I respect that about why you're private. I like that about you, I think it's nice that you're private and you know what, it's admirable. I'm just a little bit suspicious at the fact that we're getting real close and I don't know much about you.
"Every time we speak, you're like 'I can't say, I can't disclose that this, I can't disclose that.'
"And I'm getting a little bit cautious of who I'm getting close to. because I don't know you."
In this evening's episode, Kay and Lewis F's relationship took another turn when they get into a nasty argument in the bedroom.
Kay accused Lewis F of making 'a big deal' out of a planned prank, prompting him to snap: "You cry everyday about everything! How dare you say everything's a big deal to me."
Kay responded: "I'm starting not to like you. I feel you're becoming very negative. you harbour so much ****."
Lewis reacted: "You're the most unstable person in here. You're a hypocrite."
Kay said: "You clearly have a lot of issues. You're a very angry individual."
At the weekend, housemates nominated in the Diary Room for the second time this year and the results will be revealed tonight.
Meanwhile Akeem has a confession for the house as he insists he's not playing a game.
Big Brother 2018 airs Sunday-Friday nightly on Channel 5 at 10PM.