One other place to clean -- the headrest in the car. Really easy to do back and forth transfers that way. Also, all pillows and stuffed animals need to be taken care of. Stuffed animals can be put in an airtight plastic and stored for a month.
If no one else in your home has lice, the odds of her getting them from your home are slim, but you are right that she'll bring them to you. She could have gotten them from your friends or some other kids while with you. That being the case, unless grandma and ma really took the appropriate steps, they now have the lice and need to really clean their stuff! (Turn about is fair play, isn't it?)
