Depends on the age. My bonus mom came into my life when I was 4. Even then I called her by her first name because I had a mom. 26 years later I still call her by her first name. She never pushed. She was always respectful regarding my mother if I was around. She took interest in my hobbies and tried to do them with me. She called me her “chosen” daughter from the start and never tried to hide the fact that I was the child from my dad’s ex wife.