The 19th-ranked Mladenovic, who ousted two-time defending champion Angelique Kerber on Thursday, next plays last year's runner-up Laura Siegemund. The German wild card advanced to her second final in her hometown with a 6-4, 7-5 defeat of fourth-seeded Simona Halep.
Sharapova, who tested positive for meldonium at last year's Australian Open, had been given a wild card to enter the Stuttgart event after losing her ranking because of the ban.
The five-time Grand Slam champion is now turning attention to tournaments in Rome and Madrid before potentially appearing at the French Open.
“I'm moving in Europe in the next couple of months and this is what I want to go through. I want to go through the matches. I want to see how my body responds, how I feel. I want to feel that match play, I want to feel the tiredness of match play,” Sharapova said.
“That's what I asked for. That's what I wanted and I'm doing it.”