Leyla and Go!, her sister, absolutely refused to befriend any other female rat. Once, after a great amount of effort and a lot of pain on everyone's part (and much glue) I actually got them to mingle with a group of existing older girls. Some of that group should have lived as long as Leyla and Go were expected to live. I went through the anguish because pairs as close as those two were tend to take the departure of the other very seriously and, regardless of health, the other tends to follow suit.
They didn't live as long as expected. Meanwhile Leyla & Go! played pit-viper with the humans if they dared to get close to the cage wires while they were on guard, waiting (and they were always waiting).
Those girls passed on and once again there was little we could do to get these two nuts to even try to be social with other ladies. But they were getting on in rat years and at 2 years 2 months I didn't figure they'd have much longer anyway.
No luck. At 3 years and 2 months both were still with us. Of course at around 2.5 both were completely blind and had very little use of their back legs. While Go! refused to let go of her independence and would spend an hour if need be to hike herself up to the top-most floors of the cage, Leyla took the more relaxed approach. Of the two she lost her sight first and learned rather quickly that the spoils were many. One would never believe either of these two little old ladies were related to the beasts of yore.
And they were finally willing to assume a less dominant position as well. Unfortunately Leyla is alone now, but she doesn't mind. She wants her breakfast, her dinner, her baths and scratches and ear cleanings. And if Popki and Monki want to be bratty and elitist, so be it! She knows, after 3 years, that bratty and elitist doesn't have nearly as many benefits.