As the bride, you get to make every decision, even if someone else is paying for it. But—and this is a big, important but—you should be kind and gracious, using your bridal powers wisely. When you talk to his mom about what to wear for the wedding, make sure it's a friendly chat. No need to feel awkward; she'll (hopefully) want to take direction from you since it's your wedding vision on the table. Here's how to make the talk about to wear move smoothly.
Pick the right time.
If she's easygoing or into fashion, there's probably not a bad time to talk wedding-day attire. Otherwise, choose a time when you can talk privately—discussing dos and don'ts around the dinner table will turn your conversation into an unwelcome open forum. Better options: Meet for coffee to have the fashion chat or FaceTime her at an agreed-upon hour.
Give her specifics.
Just as you did with your mom, let your future mother-in-law know if you have a color you want her to wear in order to coordinate with the bridesmaids' dresses. Or if you have certain colors you'd like her to avoid, let her know. If you've got a dress length in mind (cocktail, floor-length) or style (formal, casual), bring it up.
Point out that your mom will be calling her.
She and your mom need to coordinate their outfits with one another so they look like they're part of the same wedding. Let your mother-in-law know that your mom will be getting in touch about her dress selection in the upcoming days.
Keep her personal style in mind.
Some women haven't worn a dress since their own wedding 30 years ago. If she's one of them, she may balk at your edict to wear a gown. Could you compromise and let her wear a dressy, flowing pantsuit in a luxurious fabric? You want her to be happy and comfortable so when she smiles for the camera, she means it.