[M24/F18] Had sex with my best friends little sister.

Okay, about a week ago I posted in /r/advice and /r/casualconversation about how I was caught checking out my friends little sister. Let's call her Jessica and my best friend Ben cause I am not posting their real names, even though I am on a throwaway. I got some good advice from some dope redditors and I made my decision.

So a TL;DR up to this point is that Jess caught me checking her out after a shower, called me out on it and told me I should've made a move and followed her into her bedroom.

So my mind was racing, I messaged her here and there throughout this week, three times in total. Nothing crazy, just things like, "you gonna be home this weekend?" I call her place home cause I am there pretty much every weekend. This was on Tuesday.

She said, "ya."

One word. I said, "oh, cool, I'll probably see you around."

"K."

WTF. I was getting one worded by an 18 year old girl! I felt so stupid and little. So I just said, "KAyyyyyyyyyyy" and that got an angry face back from her.