How do I get rid of someone without technically doing anything that would qualify as a felony in any court of law (please note that misdemeanors do not bother my moral character)? Because, and this is a reference to an earlier question asked, in this circle, I am on the side. And the origin is one of my very close, very male friends... we'll call him A. And on the other side of the circle is this girl that is not a very close anything, much less friend... we'll call her B. So B 'likes' A. But she 'liked' A before. Led him on for months and then broke the poor kid's heart in two...thousand pieces. SOOOOOOO, in order to prevent the example above from recurring (because a sad, depressed A is not very fun at all), I need a way to dispose, for lack of a better word, of a certain very upbeat, very annoying teenage girl. Your assistance is much needed and appreciated.
I wish I had some totally sly way to help you out, Sparkler. For the record, I can't see anything in the criminal code that prohibits you mailing someone a live beehive. Also for the record, I am not a lawyer, and furthermore I am not a beekeeper, so if you wind up shrieking and covered in bees as the cops drag you to jail, don't come crying to me. (I will probably be in jail next to you for receiving an e-mail about "How do I dispose of a teenage girl.")
Anyway, I would have millions of responses—or at least ones of responses—on how to get rid of some extraneous group member whom nobody likes, but your issue is complicated by the fact that B and A were once involved. Or at least A wanted to be involved with B? You are thin on the details here, but it seems like the dude liked the girl, and then she was all like "PTTHTBT NOPE" and fled the scene? And now she's back? Whatever that relationship was, or wasn't, it makes this more complicated than if B were just some dork you could push into the river when nobody was watching.
But if you really want to get rid of an unwelcome hanger-on, there are a few ways to do so, like:
Creating an inhospitable atmosphere. Technically, you could just be so stealthily hostile to everything this girl says or does that she finally realizes she's unwanted. If she's like "Hello!" you could be like, "Siiigh," and roll your eyes so hard and so earnestly that she is shamed into never coming around again, or you dislocate an eyeball, whichever happens first.
Confronting her directly. You could always approach the girl and ask her what, exactly, her intentions are with this gentleman. If she says something like "I like this boy and he is my friend!" then you have your answer; if she's like "I want to consume his brain because I am a space alien," then you also have your answer, and are correct to be suspicious.
Talking to the guy himself. Clearly B is here for A, and not for you, since it seems like you would feed her to piranhas at the earliest possibly opportunity. So ultimately, the only way she's going to go away is if the dude doesn't want her here anymore. Your natural tendency will be to grab him by the collar and shout "SHE IS HORRIBLE!!" and throttle him until he either agrees with you or is no longer alive, but this is not actually the best way to go about it.
In the end, this thing is between him and her. (Well, if she's being directly awful to you, then you're officially involved, but if all she's doing is wooing this dude, then it's their business.) Now, if you honestly believe that she's bad for the guy (and not just because you secretly like him), then you're allowed to present your case. But it has to be compelling. If you approach him and you're like "She's bad for you! Because of... things! And also, there is stuff!" And then the girl approaches him and is like "Look at my butt," she's going to win.
I'm not just saying that this shouldn't be your concern, Sparkler—it's good that you are concerned for your friend. But if you had a relationship that someone else didn't approve of, and that person was constantly confronting you about it, would you like that? Or would you be like "Ugh, go get stung by tons of bees!"
I think the best thing you can do here is carefully consider everything you dislike about this pairing, and explain your rational, well-thought-out argument, once, to the boy involved. If he slaps one palm against his forehead and says "You're right! I can now see that she is a gargoyle!" and never talks to her again, then you've done what you wanted to do. But if he hears your reasons and still likes this girl anyway, then that's his business. One of the hardest thing about friendships is watching other people make mistakes, but they're still their mistakes to make, and the friendliest thing you can do is support them regardless of what they decide.