Okay I live on my own with my daughter and fiancé. My younger sister who is 18 years old just got kicked out of my parents house for who knows what. She asked me recently if she could stay with my family until she can afford an apartment. I'm not sure if I should tell her yes or no. We have enough room because we live in a house. And my younger brother also lived with us for a short period until he got on his feet.
My only concern is that she finds him attractive and every time she'd come over I notice she would check him out from head to toe literally. I haven't told my fiancé about it but I actually see her do this. I trust my fiancé and she's not competition or anything but she's a pretty darn good liar. I just don't want her to try to come on to him or anything like that. That's why I want to tell her no. And if I do say yes and that happens I would blame myself because I have the say so on this one because she's my sister. But at the same time I want to tell her yes because I will be here everyday all day because I just had my daughter 3 months ago and I'm staying home with her and working an at home job. And they wouldn't be here alone period. And my mom and dad would say no because this is my family and they don't think I should ever invite another woman to live here with us whether I trust them or my fiancé or not. They believe in the don't have too many women or men for that matter in our relationship. Sounds crazy but true.
So what should I tell her?? Any advice would be nice and helpful. Thanks in advance. I just don't want to be wrong in saying yes or no. And I think we are her last option.

