Nephew test positive

My nephew tested positive and I just had a baby a week ago. My sister said her son is out of quarantine after a week but she’s been testing negative however son (4 yrs old) and dad both positive. I am paranoid and been keeping away. She calls daily and I asked if she can give us space but she said she would wear a mask around baby since she’s “ fine “ because she doesn’t believe she could be a carrier of covid and that kids don’t need to be retested for covid because they are asymptomatic but I just don’t think my sister takes covid serious because they are still out doing regular things in stores and never quarantined. I’m tired of her getting offended when it comes to my home and my kids, covid scares me I don’t get why it doesn’t scare her.