We were also thinking of Sarah Ashley. My main concern is that She may have many other girls in her class/grade/school with her name. I did when I was a kid and I absolutely hated it. Do you think that will be an issue?
I was also thinking with the name Sarah Elizabeth, we could use the nickname Ellie. My husband likes that name, and my grandma's name is Eloise, and I think it would be a way of naming her after her with out using Eloise or Louise.