The Belgian's remarkable comeback story continued on Tuesday as she came from behind to beat Kvitova 4-6 6-3 6-4 in their quarter-final.
She had slipped as low as 262 in the WTA rankings last June and this time last season had failed to qualify for Wimbledon and was playing a lowly ITF event on clay in Virginia.
That all followed a spell on the sidelines due to blood clots in her calf but such woes are now firmly behind her and she is just one win away from a Grand Slam final that few would have given her any chance of making, herself included it would seem.
"It's amazing,'' she told the BBC.
"(It's) more than a dream come true to be in the semi-finals of a grand slam, it's ridiculous."
With rain falling, the match began under the Centre Court roof and it was Kvitova who drew first blood.
The Czech, champion in SW19 in 2011, got the better of three successive breaks of serve to lead 4-3 and she was soon serving for the set at 5-4.
A lengthy game followed with several break points saved and a couple of set points also missed, one with a double fault.
However, Kvitova eventually closed out; it was the first set Flipkens had lost in the tournament.
Those who doubted how Flipkens, who has benefitted greatly from advice from former world number one and fellow Belgian Kim Clijsters, would respond were soon put in their place.
"Kim was one of the few who believed in me," Flipkens said.
"I can count on one hand how many people still believed in me and she and my sponsors are included in that."
A netted backhand from Kvitova handed Flipkens a 4-2 lead in the second set. A game later and the doctor was called onto court with Kvitova reporting she had been unwell since the previous evening.
When play resumed, Kvitova saved a set point on her own serve but it prove only a delaying mechanism as Flipkens served out to 15 to square the contest.
Kvitova appeared to have the advantage of serving first in the decider but there was nothing between the pair as the set progressed on serve for the first eight games.
At that point the Czech flinched. Some good returns put her under pressure and on break point she sent an overhead long.
Flipkens duly served out, clinching victory with an ace which needed to be confirmed by Hawk-eye.
Ten years on from winning the junior title at Wimbledon, Flipkens will now face Marion Bartoli on Thursday for a place in the final of the main event.
Flipkens added: "I still cannot believe it. I was so calm, I had nothing to lose, I just went for my shots. Petra was playing really well in the first set and I really had a lot of problems with the way she was playing and I just had to go for it from the second set on. I am so happy. You can't imagine.''
Sabine Lisicki, who knocked Williams out of the draw on Monday, continued her progression through the tournament by beating Estonia's Kaia Kanepi 6-3 6-3.
The last time Lisicki made the semi-finals of Wimbledon two years ago she led Maria Sharapova 3-0 in the first set, but ended up losing.
"I feel much fresher, fitter, and better than I did two years ago," Lisicki said.
"I'm glad that I had that experience before. I don't really remember much about it. I just know that Maria played an unbelievable match.
"It was the first or second time I played her. I think this time I'm more ready."
Lisicki will play the highest remaining seed, number four Agnieszka Radwanska, in the semi-finals after the Pole defeated China's Li Na in three sets.
The fourth seed, who almost missed the final last year due to a cold, suffered a scare on Tuesday when she picked up a thigh injury towards the end of her 7-6 (7/5) 4-6 6-2 win on Centre Court.
"I've played a lot of tennis in the last couple of days so it's been really tough, but I'll do everything in my power today [Tuesday] and tomorrow [Wednesday] to rest and put everything together to be ready for the next one," said Radwanska, who is bidding to become the first Pole to win a grand slam.