My dad just doesn't get it...:(?

My dad told me last night he wants to get engaged to his girlfriend. He knows that I do not like her very much. I tried to tell him all the reasons I don't like her, but it mostly came down to I am not comfortable with her personality. I always known her in one way and don't know if I can live with that all the time. I have to think she has another "side" that maybe I would like more, but I haven't seen it. I'm okay with her as a family friend, but I don't want to imagine her being my stepmom. My dad tried to make up excuses when I told him this like "She's given you lots of stuff and compliments" and I said "Stuff and compliments doen't make friendship." My dad says I will start to feel different if I make more of an effort to know her, but I don't really think so. Advice? I'm a 13 year old girl, btw.