How Do I Get Grandma to Agree?
Oh, dear: This is more of a relationship dilemma than a naming dilemma. At least in the U.S., choosing a baby’s name is considered a joint decision—but of the baby's parents, not the mother and grandmother. Asking for a grandparent's opinion is one thing. A grandparent who feels like she has the last word on the pick is quite another.
This is just one of the first of many parenting decisions you and your husband will have to make. A pattern of giving in to a family member just to avoid conflict doesn't bode well for the years ahead. Do you want your mother-in-law to feel like she gets to dictate other choices in your baby's life, too? Probably not.
So that means standing up for your own name choice, and your right to make it. Ideally, your husband would lead this initiative, since it's his mom! If he won't confront her in person, will he at least back you up if you do so? (If he won't: this is a bigger problem than the Name Lady is equipped to handle, frankly.)
If you are the one breaking the news to your mother-in-law, be firm, but polite and kind. You might say, "I know you love the name Raquel, and we think it's beautiful too. But we're going to call our daughter Mia." If it's true, you can add that you'll consider Raquel for the middle name, or for a future daughter. But most of all, present this as a done deal, a decision you and your husband have made together—as you will for many more decisions to come.