Basically, what we've got is another "Dumbledore is Gay" scenario.
There's more than enough room to say "they're not gay" if you look at the series alone, but the author makes an "out-of-series" reveal, which ultimately doesn't even match the character.
Dumbledore being gay isn't even wholly accurate, since asexual seems to fit the bill better. Confused as a teen, but ultimately devoid of any sexual interests as he got older (which is odd considering how often he talked about the power of love).
If anything, Dumbledore being gay as a teen is some way of insinuating that being gay is evil and leads to terrible things, since his feelings for what's-his-face lead him to ignore all the evil what's-his-face was doing.
In any case, for two girls, who've basically been straight for four seasons, to simultaneously develop "romantic" feelings in the last few minutes of the show without any distinguished build-up, is basically laughably bad writing. In fact, the LGBT crowd should feel insulted, because we've got girls who weren't "born-that-way" suddenly flipping switches like sexuality is really just a convenient choice to make.
What we've got is half-assed agenda pushing, with the grand statement of "Look, gay people can be great characters, just as long as no one knows that they're gay and it's ultimately ambiguous so we can avoid any real backlash until after all is said and done."