"I was most impressed with just her demeanour," Lewis said. "I mean you would have never known that it was the final round of an LPGA event. She played like she had been there before."
Ko became the youngest winner in LPGA Tour history and the circuit's fifth amateur champion Sunday, closing with a 5-under 67 for a three-stroke victory over Inbee Park.
"To break another record, or being in the history, it's amazing, and it's always awesome to be able to play with the pros," Ko said. "The last few holes, it got a bit nerve-racking, but Stacy Lewis, after my birdie on 15, she said, 'You know you can do it.' It was really great to have another player that I look up to giving me that much support. It was really awesome."
The South Korean-born New Zealander broke the age record of 16 set by Lexi Thompson last September in the Navistar LPGA Classic in Alabama, and is the first amateur winner since JoAnne Carner in the 1969 Burdine's Invitational.
The glove Ko wore in the final round will be displayed in the World Golf Hall of Fame.
"To have something that's mine to be up there, it's amazing, and it doesn't come down or anything," Ko said. "So it will always remain there, and it'll be a good memory."
In January, Ko won the New South Wales Open in Australia at 14 to become the youngest player to win a professional tour event, a mark broken by 14-year-old Brooke Henderson in June in a 36-hole Canadian Women's Tour event in Quebec.
Ko said she didn't cry after her victory Sunday, but did two weeks ago after winning the U.S. Women's Amateur.
"To me, the U.S. Amateur is a big event, and obviously this is a huge event as well," Ko said. "But still, as an amateur, winning one of the biggest amateur events, I feel like it was a better win — even though this one was awesome."
Ko finished at 13-under 275 at The Vancouver Golf Club, pulling away with birdies on five of the first six holes on the back nine. She opened with consecutive 68s and shot a 72 on Saturday to take a one-stroke lead into the final round.
Ko made it clear again that she has no plans to rush into a professional golf career.
"I'll still remain an amateur and then finish high school and then go to college," said Ko, who has mentioned Stanford as her college of choice. "I mean this is a great win, but I don't think this will affect me changing my routes to my career."
She was headed to her native South Korea on Monday, and will return to the tour next month for the Women's British Open.
Park shot a 69. She chipped in for birdie on the final hole, and Ko closed with a bogey to make it closer.
"The pressure she was handling is really amazing," Park said. "I'm really happy for her. It's great for her career — and I think I was just lucky to get the winner's check today."
Park's $300,000 check as the top pro moved the South Korean player past Lewis for the season money lead with $1,419,940.
U.S. Women's Open champion Na Yeon Choi, Chella Choi and Jiyai Shin — all from South Korea — tied for third at 8 under. Na Yeon Choi had a 73, and Chella Choi and Shin shot 71.
Lewis, a two-time winner this year, had a 72 to tie for sixth at 7 under.
"It was fun, though, watching Lydia play," Lewis said. "I kind of got caught up in her game there at the end, watching her play. ... Every single shot was right at the pin. Jiyai and I started laughing about it at the end. It was just really impressive and fun to be a part of history."