听力原文：W: Good morning, Uncle Smith. M: Good morning, Cathy. W: I want to have a dinner party to celebrate my birthday. Would you come? M: I'd love to, Cathy. What time? W: Next weekend, on Saturday. M: Saturday do you say? W: If that's all right for you. M: I'm afraid I'm busy then. I've already had plans. W: What about Sunday? M: I'm sure it will be all right. W: Good, you'd better come around 6:30 or 7: 00, we'll have time to chat a while. Why did the girl invite Uncle Smith to dinner?