Ladies, my sister is causing an awkward situation?

I am a 22 year old male and my 19 year old sister lives in my apartment with me. She goes to the same college as me and is very good looking. She has always played volleyball and soft ball and is in great shape. I mention is because this what make this situation so jacked up. The problem is around the house she dresses so skimpy. As soon as she comes home she puts on tiny little spanx or short shorts that the bottom of her hangs out. When I complain she just laughs and says she likes to dress like that. She has even started to wear short panties around the house in the morning. Yhey are so tight you can even make out her . She has caught me looking and instead of being made she just laughed and asked if I was enjoying the view. I do not know what to do, should I just let her continue to dress like that or should I move out? Ladies would you everr or have you ever dressed like that in front of your brother? And lastly, if you noticed your brother checking out your would you be pissed?