Playing her fourth match in two days in sweltering conditions, the rising Itawamba AHS senior lost 7 and 6 to 15-year-old Katelyn Dambaugh of Goose Creek, S.C., in the tournament semifinals.
"I just didn't have anything left," said McDonald, 17. "I felt more tired this morning than I did the day before, but I played hard. In the afternoon match, I didn't play well and she was astonishing. She didn't miss a shot."
Dambaugh was 1 up after four holes, then won four holes in a row to take command. She'll play Doris Chen of Bradenton, Fla., in today's final.
Chen, 17, was a 2009 semifinalist; Dambaugh is bidding to be the first left-handed female to win a USGA event.
Friday morning, McDonald won her third consecutive tight match, beating top-ranked Victoria Tanco of Argentina 1 up in the quarterfinals. After leading 2 up after nine holes, McDonald birdied the 16th to regain the lead.
"I felt like I was in pretty good control after the first few holes," McDonald said. "She hit the ball into the water on No. 16 and that opened the door for me."
McDonald needed 19 holes to reach the quarterfinals, beating second-ranked Ginger Howard of Bradenton, Fla., on Thursday.
"It's been a very, very long week," McDonald said. "The weather has been draining, probably 95 degrees and a heat index like it's 100 or hotter."
McDonald missed the cut for match play at the 2009 U.S. Girls Junior by a single stroke. "I thought I had a chance to win here if I could make the cut," she said. "You never want to get too far ahead of yourself, but I was playing well before I got here and my game really picked up after my practice round. My swing felt really good."
There are two more events on McDonald's calendar before the start of her senior year at IAHS - the Big "I" National Championship, next week in Chesterfield, N.J.; and the MWGA Girls Junior Am, Aug. 3-4 at Patrick Farms.