I once suggested a duo to my goto girl. She said no problem but I should be prepared to have some cut back for the fun part. I believe she does not want to let the other girl know and see what she provides to her customers for the fun part, even though they, girls, know about it. No way I shall spend double the money for some what less happy ending.
Lucky boy, OG. Apparently Crystal stimulated Luna and played an active role. Crystal is opened minded and not shy for service within her limit. If the girls also play with each other - meaning a threesome, that will be more fun and interesting.
Four hands are different from a threesome.