The phrase, "You's A Bitch" comes from an episode of the NLSS where in, NL was using too many bombs and scumming up the game. So someone in Twitch Chat wrote "You's a Bitch."
NL laughed at this response and said "I love my chat."
As a result, Ryan, took the phrase to heart using it at his own discretion.
Addtional Details and sources required.