It was a challenging week for the American as she came back from a set down three times to eke out victories. Meanwhile, the Ukrainian enjoyed the best week of her career as she reached her first major WTA Tour final in the prestigious event in South Carolina.
But she had no answer to Pegula's brilliance, as the world number five turned in a masterful defensive display that made it impossible for Starodubtseva to find a way past her.
"Thank you to the fans who've supported me throughout this whole week," Pegula said during the trophy presentation.
"There were many three-set matches. It's been such a long week for me, and you guys brought me through so many matches every single day. So thank you so much. I love playing here."
Pegula's straight-set win secured her a prize money windfall of $354,345, more than double the $164,000 she collected at the same tournament last year after a huge increase in the rewards on offer from tournament chiefs.
The win also cemented Pegula's place at No 5 in the WTA Rankings, with Starodubtseva moving up 36 places to No 53 after her fine run in Charleston.