Yeah, a "best friend" shouldn't let anything come between the friendship.
It's understandable at the very start of a new relationship, though. During the initial lust phase it can be real hard to want to spend time with anybody but that person, but you've gotta make time for friends.
Back in HS my best friend always had a g/f, or so it seemed, but it never kept us from being best friends and hanging out a lot. Sure I went and did a lot of things with both of them, but I never felt like a 3rd wheel or anything of the sort.
I don't like people who are your best friend while single then ignore you while in a relationship. When they're single again they always just wanna come back like nothing happened.
b