My daughter and granddaugther live with me, my daughter is 21. Well she doesnt like my boyfriend.?

They got into it a few months backs and he moved out....but now he is back. My daughter doesnt like this, so now she isnt speaking to me and she slamming doors, she dont want my granddaughter around me. I keep my granddaughter while she goes to work ....and she threating to move out. So what should i do.