
Those cats are incredibly cute. I recently got two new kitties, much to the chagrin of my resident cats. May I give you a few suggestions that were given to me by the shelter, who actually stopped by?
If, just as you are doing, the new cats should spend a few days in a “safe room”” separate from the resident. At this time, it is a good idea to wipe the new kitties with a towel or take their blanket and just put in on the floor in a spot the resident cat will see it. It is also good to take some of the toys the newbies have and also leave that out. The resident cast will smell it, even hiss at it (mine did)
I did not do the towel wrapping. Instead, as my picture show, I got a “fence” at Walmart (it cost ten bucks) and opened the door to the safe room after a few days. I stood by to make sure nothing happened, and in my case nothing did. I kept the door open for a couple of hours. The next day I kept the door open for about five or six hours and nothing happened. The very next day I locked up my resident cat for about an hour and a half. At this time I let the newbies out and let them get the lay of the land. This was important because they were not bothered or threatened by the resident cat.

This also meant that my resident cat would now come back to her places and have the new smell. At this time she was already getting used to the new cats. I think I duplicated this a second day.
Finally, I opened up the door and saw that there was no reaction from the resident cat to the newbies and I removed the fence. I kept my water gun handy in case there was any outbreak but was none. I was open to how much time they would spend together but they spent the whole day together.
I do not know if your cat sleeps with you now, but if she does, and even if she doesn’t, it is good to lock up the newbies in their safe room for the first few nights after they have been set free. The resident cat will be very possessive about where they sleep and where they eat.
If you are giving the cats wet food you might find it best to feed the cats five or 6 feet apart in the beginning and slowly bring the food together.
