<human>: My dad was married before my mom, and had a daughter Nicole. He never told me or my sister about Nicole, and I didnt even know he was married before. One day, she emailed my dad asking to get to know him, and they started talking. Apparently he was a shit father to her, never paid child support, never saw her. He told us about Nicole after he had met her. He was the happiest I've ever seen him when he had got back from meeting her, and he said he wants to include her in our lives.

So, she's a lot older than me and my sister, and my dad said she grew up rich. We've known about her for two years now, and she's always sending me and my sister really expensive gifts for holidays and birthdays. I don't think I have anything in common with her. I'm leaving for college next year, and it's really too late for me to just get a new sister. She's coming to visit in a couple months, and I don't want to get to know her. She's just a stranger. I don't know how to tell my dad that I don't want to meet her. He's so happy she's coming, it's all he talks about. My mom isn't happy about the whole situation, but she said she knew this would happen one day. She thinks I should just grit my teeth and do this for my dad. I don't even feel like nicole is telling the truth about my dad being a terrible father to her - he's been so great with us. I don't get what she gains from this.

Can you summarize the given text in a few sentences?
<bot>: Half sister appears out of nowhere, wants a relationship with my family. How do I tell everyone I don't want any part of this?