The glamour model, 20, was a late arrival at the villa and initially coupled with former Miss Great Britain Sophie Gradon, 30, after they shared a kiss during a champagne-fuelled date.
Sophie then put the brakes on their coupling and left Katie feeling hurt and confused, before quitting the villa to be with boyfriend Tom Powell.
That left wrestler Adam free to make his move.
And it worked! He's now coupled with Katie and they shared a kiss during their first date last week. Last night, they cosied up in the hideaway, but Adam turned down the chance to have sex as he didn't want to jeopardise his WWE dream by doing the deed on TV.
In tonight's finale, each couple gives a speech to one another about the Love Island experience and what happens from here.
Katie and Adam are the only couple out of the four final couples not to be official – Alex and Olivia make it official tonight – but they both seem excited about exploring their relationship outside the villa.
"When I came in here, I was confused and nervous about feelings and I didn't know which way to go," says Katie.
"I don't regret the journey I've been on in the short time I've been here, but when Adam gave me the chance to get to know him more, that meant a lot to me. I'm coming out of here with a smile on my face, and that's because of you."
Adam tells her: "I came into Love Island open minded. As you all know, I didn't have the best of luck. Although I had numerous opportunities to get to know different girls, I knew that they weren't right for me and she was the egg in my bag of Haribo. I'm excited to leave Love Island with you and continue the rest."
The egg in his Haribo. Oh Adam, we'll miss you metaphors so much!
Love Island's finale airs 9pm on ITV2.