Family Relationships

So I’m 21 and recently moved in with my grandma to help her out. I work and go to college so I’m independent and we have a great relationship. However, my older sister has always struggled to take care of herself and she is homeless again and she is having a difficult time finding work because of COVID. Neither my grandma nor I, wanted her to stay with us because we’ve both lived with her before and it’s just very difficult. she has been sleeping on the couch and eating our food without her “earning her keep”. I’ve set boundaries about cleanliness and other things but she doesn’t care or listen and when I try to help her, she starts yelling at me. I think that she just needs to figure this out on her own right now and there really isn’t anything I can do for her moneywise anymore… but my grandma doesn’t have the heart to throw her out. I don’t want to keep living in this environment and I’m not sure what to do.