I don't read it like that. He made the assumption that they are either a band (3) or not, and if not, he was only holding up the obligation to fulfil the booking as a solo as there really was not a duo that was ready to play properly. He did not put her out of the band. the band was not able to fulfil its oblifations by the other member who couldn't be counted on. If the other guy would have made other arangements to be there, I am sure he would have gone on as a trio. Final assesment seems that you need to either move on and find people you can count on or have a heart to heart talk with these 2 so you all know what is going on.