A breenie is a typical female character that are attention seekers. They get easily jealous for no reason towards other females in the same group that are most likely just friendly. When another female gets all the attention from guys/simps, a breenie will do whatever it takes to bring that other female down through drama and get all the attention from guys/simps for herself instead.
Female: Hi there, you seem really friendly! What games do you play? Want to play sometime?
breenie: Omg I don't like you flirting with others can you like please stop?
breenie: hEy CoMe JoIn mY gAmE inSteAd
Female: I'm just being friendly
Female: You're such a breenie!