Have you considered Brazilian names to honor her heritage? Here are a few beginning with "M."
Marabo, Marcela, Margareth, Maria Mariana, Maria-Antonia, Mirelli, Monique, Monize.
Monique is pretty, I think. However, if you live in CA, maybe Monize may be more appropriate.
Here's a site with more Brazilian "dog" names
Brazilian baby names, Brazilian names for your pet