Ostapenko hasn't dropped a set in her first five matches after the 12th seed battled past Slovakian world number 33 Cibulkova on Court One.
Speaking after her win, Ostapenko revealed she is playing with more freedom now she no longer has the pressure of defending the title in Paris, where she was knocked out in the first round last month.
"It's really great to be in the semis. I'm just enjoying being here," Ostapenko said.
"Dominika was playing great, but I'm fighting until the end and I'm gaining more confidence." Ostapenko also admitted she needed ice on her leg in between games after slapping herself with her hand in frustration at a missed chance.
"I hit myself when I missed a shot. It was too hard so I had to ice it," she added.
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