Twin Trouble

So I am 19 I have a twin sister. We have always been close. We were Homeschooled most of our lives so it was really just us. During our highschool years we were still close. We hung out with the same people. It was then I noticed that the guys were always tripping over themselves to try and get her attention. We were close enough that we talked about the boyfriend that wanted to take her virginity. I would get overly protective of her. She met a guy and were serious for a couple years. We drifted apart. But as soon as they broke up she came back to hanging out with me. We graduated and are in college. Last week her college boyfriend broke up with her. So she was upset. Someone had bought her some alcohol. I didn't want her drinking alone. We took shots. She was slamming the bottle. I went and dumped the rest of the cheap alcohol. We were both kind of tipsy. We door dashed food. We were laughing and stuff. We were watching a movie she had a headache so she asked me to rub her head. She was laying on my lap but at a weird angle. I was running my fingers thru her hair and massage her scalp. I look down and I can see down her shirt. She moves and I see her nipple I guess she wasn't wearing a bra. I looked away. Then I noticed her looking through her photo gallery. She is swiping. I see a few topless pics but she is swiping to fast. She goes back to her snap. And continue her business. I ask if I can see her phone. She hands it to me. She gets up to get more food. She almost falls down. She comes back and lays down again. I was fighting the urge but I couldn't resist. Look at the picture gallery. There were a lot of topless pic of her. And a few fully naked. I sent a bunch to my email and erased the message. My sister started complaining that she could feel a lump under her head. She sat up we watched the movie and I asked her to lean her head on my shoulder after she cried at a sad part. We stayed that was for a while. My arm was behind her back I was rubbing it. I reached all the way around I start to rub her side boob area. She didn't say anything. My finger went under her boob at one point. It was all over shirt but I know I was rubbing her tit. I swear I heard her moaning but I don't know. I hadn't ever been seen my sister like that before. But not it seems all I see is how sexy she is. Her big booty and perky tits. I feel weird. I just felt like I had to tell someone.