Opinions M31

So as of the last 4mo, my sister has been wearing very tight clothing around me and never has before, brighter colors and super tight showing off her curves and her body. Well at first I thought nothing of it until she started doing things like purposely bending over and showing her ass and print to me. Not even a foot or two away. Also she has been looking at my dick beforehand and afterwards. And it all topped it off last night when she was on the couch in really tight short shorts and I could almost see her lips. Well she got up and said she needed to go pee. She left the door halfway cracked and I heard her clearly not peeing and fingering herself hard and it sounded tight and wet asf...I thought all this was weird and wrong at first but now it makes me so hard. What should I do?