It's always the best friend...

So a guy has a best friend. She is a girl. He talks about her constantly and about how she is the only person he trusts 100% and she's so wonderful and she's such a great person. Who does he talk about her to? The girl he has been leading on for about eight months. He would never do anything with this girl; they are strictly best friends. That makes it okay right? Well what about when he tells the girl that he is kind of with that he trusts her and she is wonderful and she is a great person etc. etc. etc. What is a girl supposed to do then? Is he lying about the best friend or about the girl he is with? One way or another he is lying and I guess that is the main problem, yet when I look at myself in this situation I can't help but just be hurt by the fact that he is most likely lying to me. And I can't blame him because I have a guy friend who I would trust with my life. I can honestly say that I love him; I would do anything for him. If my guy ever came to me complaining about my relationship with my best guy friend, I would probably just get angry with him. That is what holds me back from saying anything about this best friend situation. Is it wrong of me to be bothered by it though? It's a valid feeling, right? He tends to talk about her and her characteristics a lot and I am almsot starting to take offense. Maybe I am reading too much into it, but it almost seems like he is trying to give me hints on how to change and be more like the kind of person he is attracted to. While I have always refused to change myself for a guy, I can't help but ask myself "what would *insert best girl friend's name here* do in this situation?". I hate that I am comparing myself to her. What's worse is I actually like her. She is a very cool person and in any other situation, I could see myself being really good friends with her. Not that this situation is stopping me but it's certainly affecting it. I feel stupid for worrying about this when he constantly says things that reassure me that he only has feelings for me. Then again, if he was telling the truth about that then why are we still not exclusive? I guess I understand that aspect of it, but that's a story for another time. *sigh* I suppose I will just have to deal with things for the time being...