The fourth-ranked Pegula held off a late challenge from the Belgian to seal the win on Saturday and set up a clash with world No.128 Yuan Yue in the decider.
A late break in the first set gave the American the lead, and she extended the advantage to 4-1 in the second set to all but end the contest against the 83rd-ranked Wickmayer.
"Being half-Korean and being able to be in the final here is something I can always say," Pegula said.
"Hopefully I can win, but nonetheless, it's an honour, so I'm really happy."
Pegula, with titles at Montreal and Tokyo already this year, is looking to capture her second title of the tour's Asian swing when she meets Yuan for the first time on Sunday.
The 25-year-old from China rallied to beat another American in Emina Bektas, 6-7 (3-7) 6-4 6-2. It will be Yuan's first tour final and she will also be the first Chinese player to contest a Korean Open decider.
Meantime at the Hong Kong Open, Leylah Fernandez advanced to her first final in 19 months after a 6-2 7-5 victory over fifth-seeded Anna Blinkova.
The 21-year-old Canadian raced through the first set, before finding the match-clinching break in the 12th game of the second to seal the contest in 78 minutes and advance to Sunday's final against Katerina Siniakova.
"This match was extremely tough," Fernandez said.
"Anna, she's a tremendous player, very powerful, and she's coming in with a lot of confidence. The first set I played well, the second set she started making more balls and being very aggressive. I just tried to stay calm. I remembered my coach's words to me: this is a battle, just enjoy it, have fun and put on a show for everyone."
Fernandez last played a final at Monterrey in March 2022, when she went on to win the title.
In the other semi, Czech Siniakova eased past sixth-seeded Italian Martina Trevisan 6-4 6-2. Siniakova has four career titles, the most recent coming in July at Hamburg.
Fernandez beat Sinaikova in straight sets at the 2022 French Open in their only previous meeting.
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