I'm not going to speak with my sister
It sounds like you are having an argument. Is there a reason not to speak with her?
Yes, we don't talk to each other
If you're estranged or something that's understandable. But if not, you should at least be open to talking with her, since keeping in touch with family can be important.
Oh well, I talked with her on the phone. She was saying something personal so I should talk to her in person.
Family relationships can be stressful but you are better off in the long run to maintain contact with everyone.