Jemma confesses to bedding the Chelsea footballer shortly after his split from Sarah Harding's Girls Aloud bandmate Cheryl.
The admission comes as she and Sam Thompson talk about football.
"I have worn a Chelsea shirt before, I usually go when it's freezing, it does get cold there," she says about visiting Stamford Bridge.
Jemma then jokes: "I will just ring my mate John Terry and say 'Can I have tickets?' and not go with you."
Sam replies: "You've so slept with John Terry!"
Instead, Jemma reveals: “I haven’t slept with John Terry…the only Chelsea player I’ve slept with is Ashley Cole! I used to go out with him.
"He'd just split up with Cheryl, about three months after."
Elsewhere tonight, Jemma clears the air with Paul Danan.
Yesterday the pair had a blazing row but in this evening's episode they're BFFs again - for now.
On the sofas, Paul and Jemma apologise to each other for their fight.
Paul says: “I’m so sorry I reacted that way…I miss my boy and I’m trying to do my recovery…you hit me where you hurt and I’m genuinely sorry and should have never reacted like that.”
Jemma adds: “I’m sorry for saying that too but I only said it to get your attention and it went too far…we’re like a married couple!"
But there's tension between Sam and Jemma as the pair disagree over Brandi.
In the bedroom, Jemma and Sam comment on Brandi, Sam says; “I think she’s a bit of an idiot and when you’re that age and you’re still an idiot, I don’t think I respect Brandi, I think I like her.”
Jemma adds; “She’s not a nasty person, I like her.”
Celebrity Big Brother 2017 airs tonight at 8:30PM on Channel 5.