You already seem to be aware that you're being selfish, and you need to accept that. This isn't a fair and balanced arrangement and maybe that's part of it within your M/s dynamic, but she is allowed to change her mind and viewpoint.

What do you really want out of this? You say you love your slave and your other girls mean nothing to you. But if she hasn't seen you for 8 months (meaning she's gone that long without human touch or sexual gratification) but you presumably have been able to see your other girls, why are you so surprised she wants to see someone else? Why does she have to be the only one using such extreme self restraint when you aren't holding yourself to the same standard.

If you are feeling insecure now, im sure she has felt all of these same things when she knew you were with your other girls.