Fuck a bitch is a phrase that you use when ur flabbergasted! You can also use it when somethingbad happens to you. It is overall another phrase to show immense anger.
Gym teacher: You have to run the mile right now! It’s also 5 degrees outside so bring a jacket!
A line famous from Notorious B.I.G's single "Get Money". "Fuck a bitch shit" refers to the act of not giving a fuck, having no consideration, and simply not caring about a bitch/girl/hoe.