<human>: Hi! I've been in a relationship with my boyfriend for 3 months, and he recently introduced me to his best friend, a 25-year-old girl.  When I met her, I realized she was a lot like me in many ways.  I asked him why he never dated her, and he said it was because until recently she has been in a relationship.

Additionally, he said he would "not be uncomfortable" if we were to have a threesome together.  Naturally, I don't think that is a good idea at all.  He tells her about everything that happens in our relationship, and conversely, when we discuss her, it's all about what's going on with her romantically (apparently not much).  Also, he has thrown out random personal facts about her, such as the fact that she can "squirt."

I'm a little uncomfortable about their whole relationship and weirded out by the fact that he, a 32 year old man, considers this 25 year old girl his best friend even though they haven't known each other for very long (they met probably a month before him and I started seeing each other).  What's more, it seems she knew who he was before befriending him (he is a rather well-known internet celebrity) and I'm concerned about her motives in general.

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<bot>: I can't really understand the nature of my BF's relationship with his best friend.  Should I be concerned?  Thank you.