From Yen Press:
A Brand-New Battlefield Awaits. Karen Kohiruimaki is a college student who stands at an imposing six feet. While her complex about her height makes it hard for her to make friends in the real world, the VRMMO Gun Gale Online changes everything. Now equipped with her ideal "mini" avatar and clad in a pink battle suit, Karen is ready to shoot up the world of GGO as Llenn! Before long, she meets the beautiful Pitohui, and the two rare female players become fast friends. Little does Llenn know that this friendship is the key to her entry in the first-ever Squad Jam, a team-based battle royale that echoes the famous Bullet of Bullets tournament.

Written by the gun supervisor of the Sword Art Online II anime.