Hosts Holly Willoughby, 38, and Phillip Schofield, 57, attempted to get her to spill the beans about the episode, and although Kellie tried to keep it under wraps, she did give some clues.
The Linda Carter actress hinted: "It's the most epic episode I've ever been involved with.
"I'm really excited to see it.. that says a lot."
She proceeded to give away a clue that her character may be falling into the water.
She said: "It enters around a party on a boat, on the thames.. and I get wet."
Phil said: "The grim reaper does stalk that boat."
Kellie replied with a smile, not giving anything away: "It might be me... it's exciting."
Her character has been struggling with alcohol addiction, and Kellie revealed how she researched for the sensitive storyline.
She said: "I did some research. I drank quite a lot and I filmed myself.
"Every ten minutes I would film myself.. and you could see the alcohol sort of hit me in waves as it was literally coming into my bloodstream.
"I'd repeat myself all the time, it was fascinating and a very helpful exercise."
Kellie also said she colour coded her script so she knew how drunk she had to act when the episodes were filmed out of order.
She said: "We filmed out of order so I knew I had to figure out how drunk I was going to be in the script. I gave it a colour code of how drunk I was supposed to be in the scene."
EastEnders continues tonight at 7.30pm on BBC1 and This Morning continues tomorrow at 10am on ITV