Both sentences are grammatically correct, but they convey slightly different nuances: * A. "I cut all ties with my grandma because she broke my car."
This uses the simple past tense and suggests a direct cause-and-effect relationship. It indicates that the action of breaking the car happened at the same time as or shortly before the decision to cut ties. * B. "I cut all ties with my grandma because she had broken my car."
This uses the past perfect tense, emphasizing that the car was broken before the decision to cut ties. It highlights the sequence of events and suggests a sense of finality regarding the past action. In casual conversation, A feels more natural, while B is more formal and emphasizes the order of events.

You don’t “break” a car. She crashed my car.

Preference, not enjoyment.

They are equally good. Which one to use depends on context.

Both are technically acceptable, but A is much better. Because if you're using "she had broken" you should pair it with "I had cut" else it sounds weird. And even if you use "had" in both places, it would be an unnecessarily longwinded way of speaking in the vast majority of cases, so A still sounds much better.