Why am I nervous?

I’m meeting my future sister in law this weekend. She’s 11 years old, about to go in the 6th grade. I’m in college and 19, almost 20. Her dad (my moms fiancé) is taking my mom, me, and her out somewhere this weekend. She (my stepsister) even said she wants to meet me. I’m excited because I’ve always wanted a little sister and always wanted to be like a mentor to some girl younger than me so she’ll have someone who can guide her, give her advice and just have someone to talk to. But at the same time, I’m nervous as heck. Lol this is the first time my mom’s been engaged since my dad died when I was 14 1/2. Idk why I’m nervous, this is everything I’ve wanted, my mom to be happy and to have some sort of dad again. Then I’ll have a little sister 😆. And she’s the perfect age in my opinion because I can talk to her about the teenage years she’s about to go through and stuff lol. I’ve also seen a video of her on my mom’s phone and she’s so cute. she’s hispanic and has pretty skin and a Cuban accent that I think is beautiful. what’s wrong w/ me lol?