The brother, sister shower

I’m Tom, and I’m 24. I currently live with my sister Mindy in an one bedroom apartment, so yes right away I’ll admit, we sleep together, but we wear clothes and don’t cuddle in our queen sized bed. A few months ago she broke up with her boyfriend who had been cheating on her, she moved out and really had nowhere else to go, so she came to live with me, although over the last few months she really taking a liking into me for some odd reason, I wasn’t sure what it was, but I didn’t think having a good relationship with my sister was a bad thing. Anyway as we got closer and closer, we actually started socializing with each other a bit more, going to movies and doing this and that. We got so close that one night as we were getting ready for bed, she kind of stripped down to her bra and panties as we were getting ready for bed. Oh my, she was stunning, but I was still shocked though.
“Whoa sis, why you getting naked?” I asked.
“I’m not naked, I’m just in my bra and panties, and we’re just brother and sister,” Mindy replied.
I really had no objection to that, not that I was turned on by her, I just admired her as a woman I wasn’t related to. She got in bed with me and we slept together once again, and nothing happened as always, it was normal. So we both just started getting into our undergarments before we got into bed. We did that for a few weeks and then all of the sudden one night at the 3 month anniversary of her moving in, she stripped down to nothing before she got into bed with me, and she acted as if it was completely normal.
“OK sis, what the hell are you doing?” I asked.
“Nothing, just getting ready to go to sleep,” Mindy replied.
“But you are nude,” I said.
“If I really make you that uncomfortable, I’ll put my clothes back on, but I feel we’re mature and close enough for it not to be a problem,” Mindy replied.
Well, she had me there.