The Tracy Beaker actress will battle it out in tomorrow night's live final with Denise Van Outen, Louis Smith and Kimberley Walsh.
Harmer explained that her journey on the show with professional partner Vincent Simone has been highly "emotional".
"I'm really excited. This week has been crazy, exhausting and very emotional for me," she told The Sun.
"You put your heart and soul into these dances and you just want to do your partner proud. So tensions run high and there have been a lot of tears.
"It comes mostly from frustration because I can't get the hang of a step or a lift. And I've been juggling Strictly with panto rehearsals.
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"But to be in the final is a dream come true. It means we have taken this experience as far as we possibly can – and I am so happy about that."
She added that she was surprised to have reached the final, saying: "Things like this normally don't happen to me.
"I'm just a normal girl from Bracknell, so I don't tend to be wearing ball gowns and performing in front of millions! I don't want it to end. But I know where Vincent lives, so I'll knock on his door and force him to dance with me."
The Strictly final airs on Saturday (December 22) on BBC One.
Strictly semi-final - in pictures: