Karnes, who started every game in her career, finished third all-time at Yale in points (77), fourth in goals (30) and fifth in assists (17). As a senior, she was named first team All-Ivy, second team NSCAA Northeast Region and Soccer Buzz Northeast Region first team. She was second on the team in scoring with 19 points (7 goals, 5 assists). Her goal with one second left in the second half lifted the Bulldogs past Duke in the second round of the NCAA College Cup. As a junior she was named first team All-Ivy and first team All-New England after she tied for the team lead in goals (6) and was second in points (17). She tied for eighth in the Ivy League in goals and was ninth in points. Against Cornell, she scored both Yale goals in a 2-0 victory. She had a goal and an assist in wins over Penn and Rider. As a sophomore, Karnes was named second team All-Ivy, third team all-region by SoccerBuzz and team MVP after finishing sixth in the league in points with 21. She also tied for sixth in the league in goals with nine, four of which where game-winners. Against both Quinnipiac and Fairfield she scored twice. As a freshman she was fifth in the league in scoring with 20 points and was named honorable mention All-Ivy. Her eight goals tied for third most in the conference. Against Central Connecticut, she scored twice, and in her first career game, she scored her first goal. Karnes was a two-time all-state selection at Westside High School, which was the Nebraska runner-up in each of her four years. She also was the MVP of her club team in 2000 and was named all-division three times. In addition, Karnes played tennis and was the state champion in No. 1 doubles.