Was I wrong?

Right so let me just set the scene. I am 16 from the UK and a have a girlfriend I love very much for 3 and a bit months. I was at a party a few weeks back and when the 9 of us who were not drunk decided to go to bed at 4 in the morning there was one couple on one sofa me on another and 5 people on the floor with now no space left on the floor. I am sure you are clever enough to realise that this leaves one person. So the one person was a girl who is relatively attractive and single and I share my sofa with her with no thoughts of getting with her at all and in the end a few hours later nothing had happened between us. But the other people there joked at how they were going to tell my girlfriend and now I feel terrible about it. So my question is, is what I did wrong or am I overthinking? Please any reply at the moment would be very much appreciated. Thanks in advance. (sorry if this is in the wrong forum. Wasn't quite sure which one to put this in )

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