Search Results: friends sleeping with same guy

So, my girl suddenly went for lunch / dinner with her friend, saying that she had to get some items from him that he bought in England for her relatve. They talked about his ex and how they practiced martial arts with another couple. And the dude complained that his ex was a very jealous girl and would get mad at him for even talking to another girl. So here's the question she gave him:

Would you prefer a jealous girl that's obsessed with you or an extrovert which would hang around with other guys?

As I know her, she's the jealous type, on the lower end of the spectrum and that more or less likely merely insecure.
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But then to me, its also a subtle statement that if I leave her for another, they will most likely be sleeping around with other guys.
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And then she told me that they Used to be REALLY CLOSE FRIENDS but 'something' happened, (unsaid: they no longer are, but she kept the dinner idea from me till the last minute) and that he told her that he was bullied really badly in a certain type of school when he was young.

*she taught the same type of school and he went to VISIT her and STAYED in the CLASSROOM. he started to curse the students, teachers et al.

Then she got a SMS text message (not WhatsApp) from a number that she hasn't saved. They even spelt her name inccorrectly, and she does not recall she had talked to anyone about the certain museum the sender was talking about.
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But then she was like, oh it should be A or B (another friend who's married but fancies her like crazy), quickly, search online for this museum, i'll tell him. But she has never told me to seach stuff in such a tone and was never that enthusiastic about people asking her stuff.
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Do you think that guy means something special to her? Thank you very much in advance for your opinions and

Some background, my girlfriend is 19 and I'm 22. I've been with my girlfriend for almost 8 months now and it's honestly been the best time of my life. We've had our highs and lows, but we always seem to work through our issues. Until recently that is. The other night my girlfriend, her female roommate, and my GF's "close friend" slept in the same bed together. She told me laughing because she thought it was amusing that they all were drunk and just passed out. I told her I was not comfortable with her sleeping in the same bed as another man, period. I finally let it go because her friend was in the same bed etc. My girlfriend then proceeded to tell me even if it was just her and another guy I should be ok with it. I made it very clear that I would not be and that I would not tolerate it. We argued intensely and she basically told me that she's always slept in the same bed as her guy friends, and that I would simply have to get over it. Then, yesterday, she tells me that Saturday night she, her same female room mate, and the same guy friend went to a party. At the end of the night the three returned to my GF's house and went to sleep. This time the female room mate slept in her own bed and my girlfriend and her close guy friend slept together by themselves. I took this as a complete slap to the face since it was only days after we had argued about it. My question, am I wrong for feeling this way? I turned the tables and asked how she would feel and she responded that she would not mind. I'm firm in my belief that no other man should be in my GF's bed, to open one's self to situations that lend themselves to suspicion shows me that she does not respect my feelings. Thoughts?