text: The Czech is playing in only her second tournament since she was stabbed by an intruder at her home in December.
  The two-time Wimbledon champion, 27, returned at last month's French Open, where she reached the second round.
  Kvitova will play fellow Czech Lucie Safarova in Saturday's semi-final.
  Seventh seed Kvitova was dominant in Friday's first set but was broken as she served for the match, before winning it on a tie-break.
  "Both of us play really fast on this surface," she said. "The grass suits her game as well, so it was about one or two key breaks in the match."
  Safarova came through a marathon contest with Australian Daria Gavrilova, triumphing 6-7 (4-7) 6-3 7-6 (7-5).
  Sixth seed Garbine Muguruza is also through, after Coco Vandeweghe retired from their quarter-final with the score tied at one set all.
  She will next meet either Australian Ashleigh Barty or Camila Giorgi of Italy.
target: Petra Kvitova reached the semi-finals of the Aegon Classic with a 6-4 7-6 (7-5) win over France's Kristina Mladenovic as she continues her return from a career-threatening hand injury.