One of her quotes "Don't call me Auntie Bar ! I'm not that old !" is a Japanese word play on Bar-san (Miss BAR) and Obasan (Auntie, usually refering to an older woman )
M1918 BAR also used for Anti-Aircraft weapon against incoming japanese fighter/kamikazis. The 40-round magazine was added to fulfill it's AA role, although 7 rounds was sufficient enough to shot down incoming fighters which implemented by Polish Army and using stationary bipod.
In this case, the CG and chibi sprite should be M1918A2, whereas M1918 doesn't adopt shoulder plate and implemented by later model. In addition, M1918 handguard covering both barrel and gas cylinder tube while M1918A2 handguard only cover the gas tube.
Some player call her as 'poi' duplicate. Her hair style resembles with Japanese Navy Destroyer Ship, Yuudachi in Japanese Browser Game Kantai Collection(KanColle). AC130, the official GF 4-coma creator, put some Yuudachi reference in his 4-coma in his pixiv. However, at in-game loading 4-coma, those reference was removed due the copyrights.[1]