Haddad Maia won 12 straight matches on grass including back-to-back singles titles in Nottingham and Birmingham over the last two weeks.
The 14th-seeded Kvitova reached her first final of 2022 and first grass-court final since Birmingham in 2018.
Kvitova earned the only service break of the match to begin the second set against the Brazilian.
The Czech player's only career loss in five grass-court finals was to Marion Bartoli at Eastbourne in 2011, when Kvitova went on to win Wimbledon for the first time.
Ostapenko was the 2017 French Open champion and 2018 Wimbledon semifinalist.
Fritz beat defending champion Alex de Minaur 6-1, 6-7 (5), 6-3 after Cressy outlasted British wild card Jack Draper 7-6 (5), 6-7 (2), 6-3 in the other semifinal.
Fritz is an American who won the Eastbourne title in 2019. He's ranked No. 14. Cressy is 60th. The final will be their first meeting.