The trouble with cats is they are just like us when it comes to 'friends'. Some (few) are very sociable - getting on with all. Some (most ) hate other feline competition. Also while you may be friends with many people you may not want to live with any on a permanent or even a temporary basis! You can never tell if you are going to get along with someone until you get to know them.
Feral (wild) cat populations follow a pattern which reflects how our cats would 'prefer' to live. The female lives in a static home territory which includes enough resources for her to raise her kittens. She may live with some of her female relatives, mother, sisters or daughters. This is because it gives her genes the best chance of surviving. The females may raise their litters communally, suckling all the kittens in the nest. The tom holds a much larger territory which encompasses several female's. He visits these periodically to breed.
Think very long & hard about why YOU want another cat. Your cat will be very happy just as she is - an only cat - because this is what she is used to. You say she is already territorial around the house - this is because she doesn't feel secure in the new place yet. Is another displaced cat really in her best interests? Use fishing rod style toys to play with her to avoid scratches/bites - they are accidental after all? Or maybe you have psyco kitty like me - she bit my finger this week - thought it was a sausage (for the dog)! Not all there in the brain dept!