My twin sister and I became closer than ever (PART 8)

Reminder: I'm M20 and she's F20. I previously said that we were going to be alone at home for a long time. And it kept driving me crazy she would never wear pants but only thongs.

Obviously, I had to bring the issue about her being in panties all day. She looked me up and down, and gave a pat on my crotch, "Doesn't seem to bother you". I reminded her again we're siblings, but she ignored me. I was able to realize that she doesn't want to discuss this incest morality anymore, she has her own moral code. Then we talked about my girlfriend, she asked me to bring her over for a couple of days. I told her she's probably busy (in reality, my sister being a semi-lesbian, she's very capable of hooking up with my gf and I didn't want that because my gf also had a small lesbian past)

However, my sister took my phone and without asking, texted my girl "Hey I'm alone with my sis! Come over!" to which the gf replied, "by the end of the week, sure!". Great, my bisexual sister who only slept with girls is now meeting my bisexual girlfriend who also slept with a girl. I know some guys would say this is heaven, two chicks one bed. But no, I absolutely didn't want my gf to MEET my horrible sister. No good can come out of this.

The same day, we ended up watching a movie together on the couch. She put up a lesbian movie (wtv she likes ig), it was D.E.B.S, actually I got pretty intrigued by the plot more than the lesbians. My sister almost didn't watch it, she only watched during sex scenes to openly touch herself, which I politely tried to look away. Towards the end of the movie, she decided to drop her heavy butt on me. Instantly got me a boner and it immediately got inside her kitty despite my pants fabric. I knew it cause I heard her with very small moans. She also removed her top and kept her bra. She asked me if I could unlock her bra and if we could sleep together.

After executing her orders, my moral dilemma came back, am i really sleeping with my naked sis?

(Part 9 later)