Well that is a good point.  I did assume and that can always get me in trouble.   To answer the question of what tipped me off.  She was dressed as if she was headed out for a show or dinner...., dress, high heels, make-up and her hair was not a mess as if she had been out all night.   She could have been an employee of the casino, but the dealers did not seem to recognize her.  So I assumed she was a provider.