I sometimes call my sister my cat's name
Why would you instigate trouble with your sister?
I don't know it just comes out that way.
It's not uncommon for people to call someone by the wrong name occasionally, so I wouldn't feel bad about calling your sister by your cat's name. I think as long as she knows that you aren't doing it on purpose to be mean then you're okay.
I guess so. I thought it was weird but I've never really been around my sister so I don't care.
No harm done. It's just a name and people tend to forget names if it is just basic.