What would you think about me telling my best friend to go deal with her feelings on her own because I'm fucking busy.
Why would you do that? Don't you want to support your friend?
Why does she have to bother me with her feelings? She can just go cry on someone else's shoulder.
You should help to support your friends when they are going through a difficult time in their life. Being there for them, will encourage them to do the same for you when you need a shoulder to lean on. Being rude to your friend will make you appear unreliable and will likely damage your friendship for good.
She also gives me attitude whenever I need her help and as the old Yiddish proverb says, "Is not good to be buddy-buddy with a cunt."
Is that really an old Yiddish proverb? Anyway, if you still value your friendship then you should try to support her when you can. Friends should be there for each other and if you feel she isn't supportive of you, you should eventually let her know.