Hi Helius. Welcome to the forum and to your two girls. This must be so upsetting for you, especially when you'll also be worrying about them getting over their operations too.
It sounds as if they may be experiencing re-directed aggression, which is something that can happen sometimes when cats have been hospitalised, or to the vet, or to the cattery - or when something is different or frightening, and the cats perceive each other as the problem.
Probably the best way to try and tackle this is to go back to basics, and treat them as if they were entirely new cats being introduced for the first time. This could take weeks to work, so be prepared for a long haul.
Ideally, you'll need to be able to keep the two cats separated, each with its own "safe space" with a litter tray, food, water and a box or bed to retreat to.
Try putting a Pet Remedy plug in in each of the cats rooms to help calm them down, and to use Zylkene in their food for a little while (this can be sprinkled in to their food, and seems to be highly palatable. You can also buy Pet remedy spray which you can spray on furnishings, your hands and other household spaces. It's safe if it gets on you cats, so no worries in that respect.
We took on two semi ferals in November, who have been a bit of a challenge, but the plug ins and the zylkene were a godsend in helping them to grow accustomed to their change in circumstances. Patience is also a big help.
I would use two clean cloths to rub each cat with, round its face, paws and the base of its tail, where their scent glands are located. Those cloths can then be used to "scent swap" and to get each cat used to the smell of the other again. Similarly, you can "site swap" when you let one cat explore the other cat's space, when that cat has been removed to elsewhere in the house, and vice-versa. Continue to keep them apart at this point.
When each cat has settled, then you can begin to try feeding them on either side of a closed door, so they can smell each other. The idea is food is a motivator for tolerating the smell and presence of the other cat on the opposite side of the door.
The food can be moved nearer to the door each time. The aim is to get the cats to eat as close to each other on either side of the door as you can, without them reacting, and eventually to open the door by just a crack to begin with, so long as neither cat reacts aggressively. If they do, then you have to retreat to the former acceptable distance.
The cats set the pace with this. When you can open the door, and have the cats eating comfortably without reacting then hopefully things should be a lot calmer.
Playing with the cats separately will be helpful too, as it will help to use up their energy which might otherwise be directed elsewhere - ie in the form of a spat with the other cat. Eventually you should be able to encourage them into joint play again, and this will help to distract them from the desire to fight, but again take it slowly, and let the cats set the pace.
You might find these links useful.
http://iheartcats.com/jackson-galaxys-6-steps-to-properly-introduce-cats/http://jacksongalaxy.com/2014/07/08/cat-mojo-how-to-introduce-two-cats/http://www.wayofcats.com/blog/dear-pammy-how-do-i-be-the-boss-of-cat-town/32308http://www.catbehaviorassociates.com/pams-think-like-a-cat-reintroduction-method/Let us know how you get on. What are your girls names, and can you tell us some more about them? We love piccies too if you have any to share.
