It was the fourth match victory in three days for McDonald, who last month was the first female to win a MHSAA championship in a boys tournament while playing for Class 4A Itawamba AHS.
To win this week, she had to battle a strong field of fellow females, including the veteran Grimes, who's from Meridian.
"She beat me last year on the 18th hole on the second day, rolling in a 30-foot putt," said McDonald, an incoming member of the Mississippi State women's golf team.
On Friday, McDonald had to rally after losing the first two holes. "My swing seemed to be out of rhythm, but I took a few extra practice swings on No. 3 and it felt better," she said.
And her prospects improved after birdies on the fourth and fifth holes to draw even. "She later got 1-up again and I never took the lead until I won at No. 16. Then we tied on the last two holes."
Grimes has been involved in the last six finals at the State Am, winning three titles in a row in 2007-09.
Winning an event like the State Am first involved making the 16-player field with a good effort in Monday's qualifying round. "In qualifying, you have to focus on not doing anything stupid," McDonald said. "In match play, you have to change your way of thinking.
"If your opponent leaves the door open for you, then you have to be prepared to take advantage. If they try to close the door on you, then you have to dig in and make the shots you need."
In Wednesday's quarterfinals, McDonald defeated Megan Roberts of Arkansas 4 and 3. Later in the day, she faced a future teammate, defending State Am champion Mary Langdon Gallagher, and won 4 and 2 with a bogey-free round. Gallagher is a rising sophomore at MSU.
"She's actually the second teammate I beat this week, and my hat's off to her for playing well," said McDonald. "I beat Perry Katherine Furr in the first round of match play on Tuesday. She also played very well."
McDonald said she came into the week feeling good about her game after defending her title at the Futures Tour Championships event in Greenville. "That was a good win and I really felt good about my wedge game, which was something I had been working on."
And Friday's effort left her future coach pleased as well.
Among other events on McDonald's summer schedule is a qualifier for the U.S. Women's Amateur in Roswell, Ga. Last year, McDonald played in the U.S. Girls Junior and reached the semifinals at Pinehurst, N.C.
"I'm too old for that tournament now, so I'll take my shot at the women's event," she said.
Contact John L. Pitts at 678-1522 or email@example.com