If your best friend truly values you as a friend, then she will come around and reach out to you eventually on her own. There's no need to feel as if you're competing for her attention against her boyfriend because:
1. She will obviously choose her BF.
2. This doesn't mean that she values you any less -- it just means that she likes you differently from the way she likes her bf.
The same is true for the guy who is also a mutual friend to your social circle of friends. He might have less time for you guys now, but if he truly values his relationship with the group, then he will come around and make time for you people as well.
If they both choose to just be alone with each other and block you guys out of their lives completely, then it is their decision and really, all you can do is just move on because it's not like you can nor should be telling them what to do with their time.
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