my mom spanks my daughter

I'm 24 and I have a 9 month old daughter and my mother is convinced that my daughter does bad things to her on purpose. Example if my daughter scratches her she'll say she's trying to fight her, or if my daughter isn't in a smiley mood she'll say she has an attitude with her. We recently moved in with my parents to build credit and save money and my mom has started spanking my daughter (little taps here and there) without permission from me or my husband. Idk what to do it can be impossible to talk to my mom??