I'm not going to answer my sister's phone call at midnight
What is normally the topic of conversation between you two.
Normally we will talk about movies, music, or literature. I am not really into any of these things though.
It's okay since that is late. There should be a set of boundaries for late night calls anyway.
I want to. Why should I just answer her phone call after 12.
I agree with you. After a certain time you should just let her know that you are not going to answer the phone unless it is an emergency. I think she will understand where you are coming from when you say this.