Fucking [M]y Ex-G[F]’s Best Friend

K and I have been good friends for a couple years. She was in one of my friend groups and we were always friendly with each other. She would sometimes get flirty with me but I would always ignore it, since I was dating one of her closest friends B. B would once in a while get annoyed by how K would flirt, especially when drinking, but was comfortable and always trusted me around her.