The Lady Bulldogs (27-8, 16-2 MACJC) won 4-1 and 5-1. They have won five straight and 14 of the last 15.
Keehn relieved Nichols in Game 2, flipping the tables from three weeks ago when Nichols got two wins against Coahoma.
"They compliment each other and pull for each other," Gulf Coast coach Kenneth Long said. "That's important."
Southwest falls to 16-17, 12-6.
Keehn (So, Thibodaux, La./Vandebilt Catholic) struck out four on the way to a three-hitter in the opener. The only run was unearned.
"Nora was dominant," Long said. "Her control was excellent. She controlled the game from start to finish. "
She threw on 74 pitches and told Long she was ready to go as long as needed in the second game.
Keehn entered leading 1-0 in the fourth with nobody out and runners at the corners. She promptly retired the next three batters, and allowed only two hits and a run the rest of the way.
In the opener, Brittney Triplett (Fr, Brandon/Brandon) broke a 1-1 tie with a two-out, two-run single in the fourth.
Nichols (Fr, Brandon/Brandon), Paige Dill (Fr, Olive Branch/Lewisburg), Molly Murphy (So, Southaven/Lewisburg) and Lanae Davis (Fr, Hurley/East Central) had two hits each. One of Murphy's hits was a double.
In the second game, Kristen Sexton (Fr, Gulfport/West Harrison) had an RBI double in the second for a 1-0 lead.
Nichols, now playing right field, made a big difference in the game leading off the sixth.
"She still figured out a way to help the team," Long said. "We were only up 3-0. The game's not out of reach and she hits a long, deep home run. That helped us out with an insurance run."
After Southwest picked up a run in the bottom of the inning, Nichols got that cushion back to 5-1 with an RBI single.
She finished with three hits in the game. Sexton had a pair of hits, and Izzy Werdann (So, Pensacola, Fla./Tate) doubled.
Gulf Coast makes another road trip this weekend, heading to Northwest. The doubleheader in Senatobia starts at noon.
The Lady Bulldogs' next home game is against East Central on Tuesday. The doubleheader starts at 2 p.m. at East Central High School.
For more information on MGCCC's 10 intercollegiate athletic teams, follow @MGCCCAthletics on Twitter and BulldogLIVE on Facebook, and go to mgcccbulldogs.com.