She’s my mom.
So why not say, To Mom?
My sister and I have always called my parents by their first names. It’s always been the most natural thing for us—I think I tried calling them Mom and Dad once, and it felt weird and impersonal. When I was nine, one of my teachers asked my mom if “Ceci” meant “Mom” in Spanish, because she kept hearing us call her that. I thought, it is our word for Mom.