I had a Tortoise just like yours her name was Cookie and she never liked anyone but my youngest son who bought her for $5.00,she lived to be 18yrs and happily bossed everyone around.Two females might never like each other,but they probably will learn to accept the situation with a little hissing ever now and then
I brought a stray kitten(male) home 2yrs ago to my 2 males and my big Tabby loves him,but the other still hisses and growls at him,nothing worse than that.
Here is a pic of my current crew!!!