By European standards, it´s a big question mark why she wouldn't, with her rates - which gets better the longer you book though.
I wonder who it is that she shoots with for her own website/brand, clients?
I think because of her "status" she feels she can command such fees.
Also, that is not to say that she does not do BBFS with regular clients.
I always form the opinion that if you are regular enough, and she is comfortable enough, BBFS is possible and I am sure many do it. However, it
will never be openly advertised and you will be met a big no and potential block, at the first time of asking for it