Bridesmaid/best friend/rant

Sally
So I asked a friend to be a bridesmaid after I got engaged (1yr, 4mths till wedding) and now (3.5months till wedding) she just asked if she cannot be because her career might be taking off on a reality Tv show and might get busy.... Yet I just saw she accepted another person to be be their bridesmaid on Social media. 
I'm kinda confused unless her wedding is after the show finishes. 
She has no idea I'm upset because I was happy for her career move and supportive but later it sank in that she is not really that good of a friend any way. I some times don't feel I get my needs met as a friend. We don't see each other often because she is busy, yet we live two doors down from each other. 
I think it just kinda hurts a bit because I have always had the type of friendships that 'the girl who I would consider to be my best friend, always already has a best friend'. That's happened my whole life. Oh, once I thought I was best friends with a girl but turns out she had about 6 best friends.