I've grown to resent one of my best friends of 8 years
That is so sad? How did you fall out?
My friend thinks that she's smart and funny even though she is not.
If you feel that this is not something that you can get passed, you should end the friendship. It is not healthy to stay friends with someone if you just resent them.
I will try to focus on my resentment for her.
I think if you focus on it you might hate her more. It might just be better for both of you to end the friendship and move on.