Accidentally Hooked Up With Sister's Friend?

After college, my sister and I moved into an upscale apartment complex within the city together.

I'm a very low key guy. After work, I like to read, spend time alone, go to the gym or watch TV/listen to music. I have only had sex once and in a committed relationship in high school.

My sister is very outgoing. loud, loves to party, loves sex, drinking and goes out every night after work. On weekends, she tends to bring guys back to the apartment... and lets just say they get a little loud late at night (if you know what I mean), much to my annoyance.

After telling my sister about herself, she decided to have a quiet night on Friday night. Instead of going out, she invited her female friend Amy over to hang out for the night.

During the entire night, while I was trying to get peace, Amy wouldn't leave me alone. She tagged along with me when I went to the gym (asking me how to work the machines and what they do) and kept asking me a lot of questions while I was reading.

Towards the end of the night, my sister and Amy took a bath together (in their swimsuits) while I was watching TV. From the bathroom I heard them talking about me.

Amy was telling my sister how she thought I was hot, and my sister was telling Amy how I am celibate and unwilling to have sex (not true)! Things got quiet for a while... but then Amy and my sister came out the bathroom naked and Amy started kissing on me and putting her hands all over my body.

I really wasn't into it at first, but after a few moments... I started to enjoy it and I ended up hooking up with Amy in the shower!

After that hook-up... I kinda like Amy now, but I haven't heard from her in the past two days. Do you think she genuinely liked me? Saw me as a fling? Or only had sex with me because she saw me as a challenge (since my sister told her I was unwilling to have sex)? Is it normal to have feelings for someone you just had a fling with?
Accidentally Hooked Up With Sister's Friend?
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