scared confused

my boyfriend mom is threatening to take my baby away all because her son smokes pot ... can they take her away? I'm not smoking it so I don't understand why they would, ik a few dads that smoke it and they have a happy family. she said when she gets the baby stuff like car seat stroller etc they are staying with her cuz she don't want it smelling like pot but tbh my boyfriend wouldn't smoke it around the baby when it's here, I just really hate her cuz finally we are doing good and she wants to ruin it. You know what's funny? she didn't have a problem with him smoking it before even when I was in my second trimester! So why all of a sudden she is? I love my daughter so much and I don't want her to be taken all because he smokes it, it actually calms him down cuz he has alot of trauma in his life. so should I be worried ugh first time mamma here :(