This happened to me when I bought a rescued un-speyed 3 yr old female into the house where I had my neutered 7 yr old Queen and matriarch Tara, and 5 yr old Casper my male.....it was the new Tammy who would goad Tara to annoy her and steal her bed and blankets from under her and drag them across the floor often with Tara still in them, or she would steal her toys....both resulting in nasty fighting - just between the girlies....you are doing the right thing....I speyed the new female, and now they are absolutely fine....Yes Tammy is still a wee ASBO, but naughty as she tries to be, Tara doesn't bother now Tammy is fixed !
...Keep us posted !
Debra x x x x
1. Tammy,4.5, Casper,5.5, and Tara,nearly 8
2. Tara
3. Casper
4. Tammy