A girl who only see's the negative side of something a guy tries to do for her and is completely inconsiderate.
Billy: hey tanya i got you and drink from the bar, my treat.
Tanya: What is this!? dont you know i only drink vodka redbull!! (throws drink away)
Billy talking to his mate: See what you get when you come out with 20% bitches.
When you try and do 80% good in a situation and the person recieving the good see's that little 20% stuff up you've unknowingly made. That ungratefull bitch is a 20% bitch and never see's the good in someones actions.
Boy: Hey babez i got you a drink at the bar
Girl: Umm this isnt vodka redbull, didnt you know i only drink vodka redbull?
Boy: (turns to his mates) fucken 20% bitch i got her a drink and she doesnt even appreciate it.