Krejcikova, a former doubles world number one, believed she had won previously in the last match but had a lineup telephone erroneously overruled by the umpire.
She'll play with Russian 31st seed Anastasia Pavlyuchenkova at the closing.
"I always wanted to play with a game such as this," explained Krejcikova, who's ranked 33rd in the world.
"When I was younger and that I had been playing juniors, I wanted to play this type of difficult game where we had opportunities and were playing well - and only you can triumph.
"Even though I dropped now I would be quite proud of myself since I had been battling. That's the most essential thing, to struggle, in this and within our life"
Pavlyuchenkova's better experience helps her through
While Pavlyuchenkova hadn't played at this level before, she'd have greater expertise and pedigree compared to her 23-year-old opponent Zidansek, yet another semi-final debutant.
Pavlyuchenkova had attained six Grand Slam quarter-finals within her profession - like at Roland Garros at 2011 - whilst taking the scalps of Belarusian third seed Aryna Sabalenka and two-time Grand Slam champion Victoria Azarenka in her conduct into the previous four.
In contrast, 85th-ranked Zidansek hadn't been beyond the second round in a major.
She's never won a WTA title, nor been ranked within the world's top 50, making her advancement even more surprising.
The Slovenian, who conquer 2019 US Open winner Bianca Andreescu at the initial round, owns a heavy forehand and also the capability to play variety, teeing up an interesting semi-final which few could have dared to predict.
A fun first pair was delicately poised at 5-5 after the two players had broken function double, together with Pavlyuchenkova pinching the opener when Zidansek made a nervy double mistake on the Russian's first set stage.
After Pavlyuchenkova broke for a 3-1 lead at the second group, Zidansek appeared at risk of crumbling but fought back to break function for 4-3 if Pavlyuchenkova additionally double-faulted in a vital moment.
On the other hand, the Russian written herself to crack again in the subsequent game and functioned to clinch her location at Saturday's final.
Following Zidansek pummelled a backhand to the tramlines on the very first game point, Pavlyunchenkova showed little emotion, apparently shocked by the scale of her accomplishment and coated in sweat after a difficult struggle.
"I really don't know what to believe because I am so tired but happy. It's so emotional," she explained in her on-court interview.
