The pair played husband and wife, Nicola and Jimmy King, on the ITV soap for over a decade until Jimmy was killed off in a recent episode.
Speaking during a press conference, Wheeler said she was “absolutely gutted” when she learned about the plotline which saw Jimmy dead behind the wheel after he crashed his car.
She said: “It was really surreal.
“It sort of ends, and you go, ‘Oh gosh, that’s it’. We’ll never be Nick and Jimmy again together.
“I was gutted because I think it’s the institution that Jimmy and Nicola were, where I was sort of like, ‘oh God, that’s over’.
Nick Miles plays Jimmy King on Emmerdale
“Even whilst we were filming it all, it never felt real because we film out of sync. When it came to doing all the scenes where he dies, it was odd. It’s almost like you didn’t want to do it.
“They were beautifully written scenes, so you want to do them justice but at the same time, you don’t want them to end because then it means this is final.”
She told Miles that his character will get “a good funeral”, adding that she will miss her on-screen husband.
She said: “I can’t imagine the character would ever fully move on. I think there’s always going to be part of her that loves him. Her heart will grow to fit another love in, but she will never let Jimmy go.”
Wheeler also revealed that Kev Townsend, played by Chris Coghill, becomes a “surprising help” during her grieving process.
She said: “Something happens in which I can only say Nicola behaves appallingly, and Kev is a gentleman, and I think from that moment she starts to see him in a different light.”
Emmerdale airs weekdays on Virgin Media One at 8pm.