I'm going to ignore my stepmom because she's treating my dad like shit
Why would you choose to ignore her instead of talking to her about it?
I would like to talk to her, but I'm afraid she'll just treat me like she's treating my dad.
If you feel that your stepmom is being abusive to your dad and you are afraid of her, perhaps it would be best to have a talk with your dad.
I'm going to ignore her because it's good to ignore abusive people. Don't you think?
Ignoring won't help and your situation won't change.