I'm going to forget my best friend's wife's birthday
Why are you trying to forget it?
I told him I'm going to forget it because I think she's a bitch.
What were you trying to achieve with this behavior?
It doesn't matter, it's not like I need anything from them.
You said this is your best friend and his wife. Not sure what you mean about not needing anything from them, but I would think you'd at least like to maintain your relationship with your best friend. You should try to be less rude and judgemental.