Girls liking other girls who are rude and arrogant can most likely mean two things. Either it's because those awful girls are popular and other girls want to be like them or those awful girls are blackmailing them.
You see, nobody - not even a girl - likes people who are arrogant and rude and essentially horrible. I mean seriously, would you like someone like that? Usually when people act nicely towards those kinds or suck up to them, it's because those people want something that only those awful people can get them. Since I'm assuming that you're in high school or middle school, this thing that they all want from the mean girl is most likely popularity since people at that age are often shallow and show this shallowness (don't get me wrong, older people can be shallow too, they're just better at hiding it).
The other reason I posed was blackmailing. For instance, those rude girls could threaten other girls that she will spill their secrets if they don't become her friends or if they don't act like they like her. Once again, this is under the assumption that this is high school or middle school we're talking about where people are still blatantly shallow like this. Although this option is not so likely.
I hope this helps.
