Emily Hayden led the way for the Patriots with 12 points, while Jenna Warrick added 10 points and seven rebounds.
Petty led Southside with a game-high 13 points and four rebounds.
Bethesda will look to build on its momentum as it travels to Eminence today.
“We would just like to get some consistent games,” Lightfoot said. “With the weather cancellations and reschedules and all of that, we’d like to get in and start playing more consistently. I think that if we can get back our momentum, that has been a key for us, I think that will carry us on into the sectional.”