Apparently Charlie Sheen is not someone who lets go of a grudge easily.
His response? "Oh, that bitch."
The feud started after Rihanna allegedly refused to meet Sheen's then-fiancée Scottine Sheen (formerly known as Brett Rossi) at a restaurant three years ago.
In Rihanna's defense, perhaps she didn't want to say hi to Charlie Sheen and subsequently his fiancée because his first response to hearing a woman he doesn't get along with's name is "Oh, that bitch."
Just a thought.