The Panthers led 12-9 at the end of one, and a Jasmine Demers basket gave them a 17-13 lead late in the second, but a three from the Chargers' Lauren Link, plus two from Briley Sullivan, made it an 18-17 L-M lead at half.
Baskets and Demers and Trisha Lenhart keep St. Mary's within 22-21 early in the second, but the Chargers ran off 15 straight, fueled by four apiece from Sullivan, Brooke Runneberg and Kaitlyn Pinney, gave L-M a 37-21 edge, before Demers ended the quarter with a free throw.
Six points from Demers, and two from Lenhart, brought SM back within seven early in the fourth, and they would close within five late, but they were unable to get over the hump as the Chargers prevailed.
Demers finished with a game-high 26 to lead the Panthers. Lenhart followed with seven.
"I'm proud that the girls didn't give up," said St. Mary's head coach Jim Demers. "That was a rough third quarter, and we just fell short. We just couldn't get anything to fall. We're still giving up too many points defensively and too many offensive rebounds. But we've got another shot at them in regionals."
The Panthers drop to 4-16 with the loss and will be at Alta-Aurelia to wrap up the regular season Tuesday night.
Laurens-Marathon improved to 3-17 with the win. Sullivan led the way with 14 points and 16 rebounds. Runneberg totaled 10 points and seven rebounds, Link nine points, Allison Hofmaster nine points and Pinney seven.