I have several rescued cats. (Or should I say, they have ME...!)
They are ALL spayed and neutered.
I am also a strong advocate for spaying/neutering.
It does calm down the territorial marking and also most aggressions. It takes a bit more time for females to recover from the surgery since spaying is a bit more intensive, but they should both benefit. You're doing them a great service by getting them spayed & neutered!
I hope it helps your little girl, Acacia and her territorial marking!
I've also noticed for my cat clan, that giving the 'new' cat MORE attention since they are generally a bit more scared, etc., is part of the reason that the others will get territorial or mark. I know it has to do with their 'space', but also with their 'human'. So, be sure to give Acacia LOTS of positive attention. Hopefully, that will help her to feel secure. Sometimes territory marking is about lack of security.
Would really love to know how it goes for you.
All the best ~ Rhonda
Your vision will become clear only when you look into your heart.
Who looks outside, dreams. Who looks inside, awakens. Carl Jung