Variety is the spice of life guys. Why stick with one when you can try many? Even if you decided to try someone different at the shop why would it be of concern to the ML you were seeing before? They're all there to make money! Sometimes seeing another ML can instill jealousy in your regular to make her work harder for you and deliver more benefits. Just because you see one girl doesn't mean you are compelled to see the same girl again. Give the other girls a try and you never what might happen.

On the other hand, if you are so attached to this girl or frightened not to upset your regular then choose another day when she is not working and have your session. No dramas. Hasta la vista.