Instead of saying bitch all the time blanch is used as an inside joke and also to steer away from excessive swearing.
Normal: "What up bitch, how you been bro?"
Slang: "What up Blanch, how you been bro?"
Normal: *Spills something* "What a bitch! That's my new rug too.."
Slang: *Spills something* "What a blanch! That's my new rug too.."