The two-time college player of the year at NCAA champion Duke beat the 15-year-old Kim 5 and 3 Saturday in the semifinals of the U.S. Women's Amateur golf tournament.
Blumenherst advanced to Sunday's 36-hole final round at Crooked Stick Golf Club against Maria Jose Uribe of Colombia, who beat Ha Na Jang of South Korea 2 and 1 in the other semifinal.
'It was really fun,' Blumenherst said. 'I played really solid, hit the ball well and the putts were falling.'
Kim, of Hilo, Hawaii, had to go 21 holes to pull out a quarterfinal victory on Friday, but she fell apart early against Blumenherst and never recovered, even with a late run of four straight birdies.
'At least you can't say I gave up,' she said.
Blumenherst, who grew up in Fort Wayne, Ind., and lives in Scottsdale, Ariz., went 3-up after Kim hit behind a hazard on the sixth hole and 4-up two holes later after Kim's second shot went into the water. The 20-year-old Blumenherst, who has had only one bogey in her past three rounds, birdied No. 10 after the backspin on her second shot brought her ball within a foot of the pin, and she birdied the par-5 No. 11 after a near-perfect pitch from the sand.
She knew she had the match after that.
'I was playing too well,' Blumenherst said. 'I knew I was hitting the ball so well that I was going to par at worst.'
She was 7-under par for the round when the match ended after the 15th hole. She finished the final three holes anyway.
'I hadn't played 16, 17 or 18 since my first match. I really just wanted to get a little more practice,' Blumenherst said.
Kim, the youngest champion in the tournament's 107-year history, was trying to become the first repeat winner since Kelli Kuehne in 1995-96.
'I can't believe she played that good,' Kim said. 'I knew I was out of it. She just kept birdieing. I tried to take it as far as I could, but ... oh, well.'
Uribe, who will be a freshman at UCLA in the fall, was down one hole before Jang bogeyed No. 9. Uribe then birdied the next hole and stayed in front the rest of the match.
She sealed the win with a 55-foot birdie putt on the par-3 17th hole.
'It was hard. It had a slope,' Uribe said. 'I just wanted to make it in two putts. After I hit it, yeah, I knew it was perfect.'