Beautiful belt and beautiful jewelry choices! I don't know if I would mix them though, I think all one color metal looks a lot better, it will just look a little off. You could change the belt to rose gold but I love the silver.
I am doing something similar. I was given a gold locket by my sister that I will be wearing and a white gold tennis bracelet of my mom's. The bracelet matches my engagement ring/wedding band and I got earrings that compliment all of the pieces. I personally think what you have looks great!
The belt on my dress was silver and I’m having it removed because one of my colors for the wedding is rose gold. I got a new one. If you can’t do that, I honestly doubt anyone will notice because none of those pieces are right next to each other.