How to stop being passive aggressive?

By saying whatever in your mind literally and don’t use sarcasm.

You don’t need to argue back each time. Be more mature than she is. Don’t feel that you need to respond to everything she says. That will shut her up.

If you arguing all the time, why is she your girlfriend?

Are you actually being passive-aggressive or is your girlfriend just saying that as part of her cutting and spiteful manner?
If you are actually being passive-aggressive, speak up, as @Mimishu1995 suggests.Take the passive out of your behavior. Say what you mean.

Read up on what passive aggressive behavior is. Really educate yourself on it. And while you are doing that, start examining your behavior and what you say and her behavior and what she says in light of your new information. If you really apply yourself you will soon know more about passive aggressive than she does. There are dozens of websites and books available on how to deal with passive aggressive people in different situations.

For starters, using cutting spiteful words is classic passive aggressive behavior. It sounds like she is preempting you by accusing you of the very thing she’s doing.

Always wait at lest 24 hours after an argument to avoid aggressive outbursts. With time away from each other gives both parties time to rethink their responses and behave maturely in finding a balance in the relationship again.
Her diagnosis was a way to get you to respond to her attack to throw you off.
Maybe if that happens again tell her that you need a few days to think about it with a clear head. Tell her when it would be best to talk calmly about his and set a time to meet again .

Passive aggressiveness comes from a place of fear. It’s a way to get out your feelings without really committing or admitting that you are angry, which can result in confusion for the other person & frustration for you. Just say exactly what’s on your mind, without worrying what the other person will think or how they will react.

I, personally, am the queen of passive aggressive and couldn’t bring myself to ever say something without caring how the other person feels. So that advice is much easier said than done, I know.