I'm going to yell at my coworker.
Why are you going to yell at your coworker?
She keeps making fun of me and I'm sick of it.
If she is making fun of you then you have a right to report her to HR. You should not stoop to her level and yell at her because what if she reports you to HR? You will end up looking like the instigator while she plays the victim.
Okay... I won't say anything to her.
Not saying anything to her is a good decision. If you want to get her to stop making fun of you then I really think you should talk to your boss or human resources about it, because they'll be able to deal with the problem effectively.