Pretty sure that Raina's group called themselves "freaks" the same way that a lot of people started to call themselves "nerd/geek" or someone who is gay might accept the term "***" and identify with it. They were street kids that the rest of the world look down on, so instead of cow-toeing to everyone else's opinion they choose to embrace their outcast status. She isn't saying "I randomly came upon a large group of homeless children, all of whom happened to also be descended from the same evolutionary line", it's just her way of saying, "I fell in with a bad crowd, and (being kids) we were silly enough to think acting the way we did somehow made us different and special." I mean, otherwise, where are all these other people?
Think of how Raina constantly tries convincing Skye this is their destiny. Family (blood and created) is a running theme in the show, particularly this season, and I think in some twisted way Raina sees Skye as a sister-like figure. Now, on the one hand, Raina is a character with shifting loyalties who places her self-interest ahead of all other, but she is also, for lack of a better term, a true believer. She could very easily resent Skye or foster her obvious suspicious/disbelief, but instead she continually reinforces the connection between the two of them. If there were others like her, especially if they were people that she grew up with and lived with and was likely close to in her childhood, why not invite them to the party? She is persuasive and cunning enough that she could have set it up, but in the end it's just her and Skye.
Raina so believed that people like her deserved this "gift", I honestly think she would have reached out to any she knew, believing it to be their birthright. But in the end, I think it's more likely that the kids she fell in with called themselves freaks only because that is what they believed society saw them as, and choose to embrace the identity and that Raina brought it up mostly because she looks back on it as ironic since she now believes herself to be something grander than human.
Of course, it's not going to seem quite as amusing when she sees what she's transformed into.