My sister in law is trying to get my daugher to call her mom, what should I do?

My sister in law pretends that other people's babies are her's. Her mom's roommate has a baby and she posts pictures of herself with the baby with captions like "me and my baby" and "my sweet little man." My daugher is just under a year. She says several words, but hasn't yet said mama although she calls my husband dada. This weekend my husband took her to his mother's and his sister was there. He was filming them and I watched the video last night. At one point, his mother was messing with the camer and accidentlly started filming. My husband was obviously out of the room because I could just see his mother's feet. You could hear someone saying "say mama, am I your mama, do you love your mama, tell mama you love her." Then my daughter actually DID say mama and you heard "that's right! I'm your MAMA." Then the camera panned up and you could see my daughter and my sister in law sitting on the floor. It stayed on a few more minutes, but when my husband came back in the room my sil stopped what she was doing. What should I do?