Whether or not you're married, everyone will be happier if your partner's mother loves you. You can win your mother-in-law over by sending your love to her.
Choose a Friday evening when the moon is waxing. Take a pink candle and write your wish around it. Your wish should come from the heart. It could be something as simple as:
"(Mother-in-law's name), love me."
Take a pin with a blue head, for healing, or a yellow head for enlightenment. Between the beginning and end of your message, pierce the candle with the pin so that its tip emerges on the other side of the candle.
Light the candle and imagine the light of the flame warming your mother-in-law's heart. Leave the candle to burn down and extinguish itself, and salvage the pin.
Now have a tulip bulb ready, because tulips are said to heal rifts and reunite. Confirm your wish as you push the pin into the bulb. Then bury the bulb in a plant pot or garden. Your mother-in-law's love for you will grow with the bulb.
Source: The Good Spell Book