On the one hand I see your point about being quick to suggest finding new friends but reading into the OP a bit more, I find there is some revealing information there. First off a situation where that kind of "play" were acceptable, it would likely be between pretty tight or close friends. That's the fisrt thing that gives me the impression that this was not a group of people that she is close to. Second, that she is as baffled by the behavior as she is, also alludes to the fact that these do not seem to be people she knows well or she would have seen this type of behavior in the past. So I come to this conclusion myself. one, they are not close friends and have offended her doing what they do with each other or other close friends. In that case finding new friends or not hanging out with them is appropriate.

two, if they are indeed close friends that she knows, it brings up a slew of other questions as to how or why she has not seen this type of behavior, what about it is so out of character that she would be this baffled and offended by it . I mean, if you know people well, typically over time these things are revealed. if indeed they behaved this way for the first time, there is something else going on really and that needs to be explored.

Truth is, from our small excerpt of her relationship with these girls and what happened, none of us can really say much that would be meaningful.

In summary, to answer directly to the OP's question, it was unfair. What isn't answered is whether or not they meant harm or if it was just play that she misunderstood... I don't know there is just far too little known here to say.