<human>: Summarize the given text in a few sentences.

It started off a few months ago when during sex she asked me what I would do to another girl if she was in bed with us. I went into detail and it seemed to turn her on so it became a regular part of our dirty talk.

Earlier this year we were able to turn that fantasy into a reality and in the days that followed my GF kept telling me how much she enjoyed watching me with the other girl. She said we should try it again and I couldn't have said agreed more.

She then told me about how she wouldn't mind if I hooked up with a girl. I laughed it off and changed subjects. The next day she brought it up again and we set up some ground rules including it can't be any one I currently know, I can never talk to the girl after and I have to let her know before it happens. I never took advantage of this offer, thinking it was just a fantasy of hers.

Since then she has brought the topic up multiple times and each time the "restrictions" become more and more lenient. A couple days ago she went as far as saying there are absolutely no restrictions as long as I tell her about the sex and preferably show her a picture of the girl afterwards.

Is this a normal thing? I started thinking that maybe she cheated on me and is just trying to "make things even" so I asked her flat out and she says no. I have no reason not to believe her.

My biggest issue is that in the future she will want to have sex with another guy (even though she says she has no intention of doing that) and for some reason that would destroy me. I know that is incredibly selfish of me and I have been justifying it mentally by saying it's a turn on for her so I should just do it. Am I just kidding myself in order to sleep with other women?
<bot>: Girlfriend told me to have sex with other girls. Is it a trap? Is it selfish that I would not want her to do the same?