While helping her put on tights:
"Elese, why do you think we dress up for church?"
"I don't know."
"Is it so our friends admire how pretty we look?"
"Yeah!" (She never fails to take the bait.)
"Actually, it's to show God that we think he's important enough to dress up for. Remember last weekend when I made you a birthday cake? What if I'd just flopped the cake on a plate and put a blob of frosting on it? Would that have made you feel special?"
"Yeah..."
"Really? But what did I do? I made a cat cake that matched the cat theme of your party. I spent a lot of time on it, and I made it as pretty as I could. Do you know why I did that?"
"No."
"It's because making it pretty was one way that I could show you that you're really special. You are worth taking the time to make something pretty, and making you a pretty cake shows you that I love you more than making a cake that didn't take me any time and that I didn't really care how it looked.
"In the same way, we dress up for church because it's a way of showing honor to God. We believe that God is worth the extra time to look nice when we go to worship him. It's fun to dress up and look pretty, but it's important to remember that we're actually dressing up for God."