The fact that she has fallen in “love” with someone that she’s never met face to face(He might smell,dribble,have bad breath, fart a lot) and “can’t” wait even for two weeks to meet him means that no she isn’t mature and no she isn’t really an adult yet.
I’d go with her to check out his parents and situation,the mother could be an alcoholic,heroin addict,sexually promiscuous who has an "Anything goes "policy as far as her kid is concerned.
She doesn’t sound incredibly competent as a parent in allowing someone elses young daughter to travel to a strange town on her own to visit what are really almost complete strangers.
If his parent does actually have any sense of responsibility then she will be relieved that an adult does the sensible thing bymeeting her.
And what happens to the girl if she and the boy have a blistering row soon after arriving there and end up on none speaking terms?
Does she salve her pride by not telling her parents and spend the rest of the stay in miserable solitude?
Do her parents have to rescue her ?
Or does she "become more agreeable "to the boy so that he’ll be nicer to her?
I think that its a very,very bad idea all round.

