Kat heads home to Albert Square in a few days' time and immediately shows loyal support for troubled Jean Slater, who has been conned by schemer Michael Moon.
Wallace told The Mirror of her EastEnders return: "I've really missed it and it's great to be back. It's like going back to my family. It's fantastic.
"I've especially missed working with Shane [Richie]. He's one of my best pals. I love him dearly - I think that's why we bounce off each other so well on screen. I rang him nearly every day to check up on what was happening! I feel like Kat's come back a lot stronger."
She continued: "Before [my] break, I had the baby swap story and towards the end of last year, Kat was becoming very downtrodden. Now she's coming back fighting fit. It's almost like when Kat first arrived on screen in 2000. She's come back with those original feisty, tarty, funny and a bit cold sides to her. It's a new Kat."
However, Wallace added that fans should not necessarily expect plain sailing for Kat's marriage to Alfie.
She said: "I think there will always be love between them - they are fish and chips, they go together. But they are going to have their ups and downs, which I can't talk about."
EastEnders airs Kat's return scenes on Thursday (June 7) at 7.30pm on BBC One.