World No.4 Gauff tied her head to head record with fellow American Pegula at five apiece with a dominant 6-2 6-4 victory in Sunday's final, going through the tournament with five.straights sets wins.
"I think it's night and day, the player I was last year to now," said Gauff.
"I don't think that this is an indicator that I'm going to do well in New York. Just knowing the quality ones that I had this week, hopefully I can use that experience."
Pegula had also reached the Washington Open final earlier this month but 22-year-old Gauff was too strong and surged to a 5-0 lead in the opening set, breaking twice and capitalising on her compatriot's double faults.
Pegula, who ousted defending champion Iga Swiatek on Saturday, broke Gauff without dropping a point at 5-2 but was unable to recover from the early deficit against the power of her opponent's forehand.
Two-time grand slam winner Gauf rapidly took a 3-0 lead in the second set, breaking in the second game while taking advantage of the 32-year-old's failed returns and went on to claim her 12th career singles title.
Gauff will head to New York for the start of the US Open next week seeking to emulate her breakthrough triumph in 2023 when she downed Aryna Sabalenka 2-6 6-3 6-2 in the final, becoming the youngest American winner since Serena Williams in 1999 at age 19.
"I thought she just played at a really high level and didn't really have many dips," Pegula said. "I didn't really think I played bad.
"The more you construct the point (against her), the worse it is because she almost likes to run. It was tough today.
"A dangerous, confident Coco is going to New York."
- with the AP
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