Petra Kvitova reached her first final since making her comeback from injury after compatriot Lucie Safarova retired hurt from their Aegon Classic semi-final on Saturday, while Ashleigh Barty stunned Garbine Muguruza in the other last-four clash.
The Czech only returned at the French Open after sustaining serious injuries to her left hand last December when an intruder broke into her apartment and attacked her with a knife.
But the two-time Wimbledon champion is now one win away from a maiden Birmingham title after Safarova pulled out with a thigh strain at 6-1 1-0 down.
"I was just thinking about my game and I'm sorry for her that she's unhealthy, but I hope she will be better soon," Kvitova said. "I think she had a great run here for sure.
"I'm happy that I'm in the final, but the way I am going is a bit weird. The hand is good, which is the best news which I can have, and I am not feeling any pain, and that's the best news.
"I couldn't have imagined to have a better comeback than I am having now. Paris was a bit weird and strange and I couldn't play the best over there. I am happy that I am able to show good tennis here."
World number 77 Barty, meanwhile, qualified for the biggest final of her career by coming from behind to beat former Wimbledon finalist Muguruza 3-6 6-4 6-4.
Discussing her final opponent, Barty said: "I don't think you can find any tennis player at all who isn't happy to see her back and genuinely pleased she's back on tour and being successful.
"She's one of the nicest girls you'll ever meet, not just in the tennis world. So it's so nice to have her back out on the court.
"Obviously it's a big challenge for me tomorrow. She's won Wimbledon a couple of times and is amazing on grass court as well. So it's going to be a good battle for me."