First of all, I apologize for my spelling, English is not my first language.

I have one friend who is in a open relationship (the have sex with other people and they seem fine about) with a guy from other city. A few days ago, he came to visit her and we all went out for a drink. Later that night, we went to my friend's house (I was going to sleep there because my house is too far away) and, while we were watching some funny videos on the internet, he started to caress me. My friend noticed it but she did nothing, and she also didn't seem unconfortable about it. Then she went to sleep, leaving us (and other friend who was also staying in her house) alone. Then, when we all were going to go to bed, his boyfriend came to my room and we started to talk... and then to kiss. I was worried, so I asked him if it was OK for us to have sex, and he assured me that my friend was OK with it (I'm not sure if he meant that she was OK with him having sex with other women or having sex with me specifically), and finally we started to have sex.

While we were doing it, someone knocked the door and a second later my friend was in the room, seeing us totally naked and not in a very flattering position. She seemed surprised, but not mad. I was totally embarrassed but her boyfriend was cool with it and he didn't stop to do what he was doing. As I was shocked I didn't know how to react, so I just did nothing... and then my friend said that she wanted us to keep having sex... while she was watching.

And we did it.

But the next morning she started to behave in a different way. She started to look at me with a strange face and to make very hurtful jokes about the theme. She even told me that she was going to tell the story to a mutual friend.

And now I feel bad... awful. I don't know if she is mad about it or if she is just trying to make me feel bad about it, just for fun. I don't know if she is sad... she keeps telling that she is OK, but the jokes are just too much. I don't want her to feel sad, I don't want her to have problems with her boyfriend... and I also don't want to lose her friendship. I feel that I should have known better and do nothing but sleep in that house... but, on the other hand, the situation is just too strange for me to understand...

So, here is the question: What I did... was it as bad as I feel it was? What should I do about it?

Thank you very much.