Sister still leaving house while pandemic going on, what would you do?

My little sister lives with my mom, her dad, and my other little sister. She snuck out today to go to her friends (she’s 17) nobody in the household has left because my mother and stepfather both have health issues. My stepfather has a seizure disorder, high blood pressure, and diabetes. My mother has heart issues. My mom doesn’t want to let her back in the house cause she doesn’t know where she’s going, who she’ll be around, or what she can bring back. My stepdad thinks it’s wrong to keep her out when she’ll eventually want to come back. She’s done this before hit it was before the pandemic started. They don’t have an extra room to keep her away for 2+ weeks so that isn’t an option. What would you all do? I agree with my mom.