No, your friend was wrong to say that. Your mom cannot ever be replaced, nor will the pain go away because there is another woman. My mom died when I was 6, I'm 18 now. I still think about her occasionally and definitely still miss her. It's not wrong for your dad to date and find another person, though. And it's great that she's nice to you and your siblings. It's understandable that you don't get along with her or don't really like her. If he stays with her, hopefully in time you will warm up to her. But she won't replace your mother. She didn't give birth to you, or nurse you, or raise you in your childhood. Only your mother did, and no one can change that.