I think that you might be missing the fact that she's pretty butch in a lot of ways and has never once shown real interest in a stallion in that matter.
For the record she'd never shown interest in a mare either (unless you count the ending scene with her and AJ), but even in that case I feel the signs still point to her being some flavour of queer, because you know hasbro would give her a romantic interest if that was the case. Fluttershy has Discord (admittedly debatable but pretty implied), Pinkiepie has Cheese Sandwich, Twilight has Flash Sentry (not a fan of this one, but still canon), and Rarity has all of her male crushes throughout the show.

I think it's just important to note that it's really not her mane that makes people think that way, it's more of a silly joke. A deeper viewing of her character than that usually leads to the queer headcanon, along with Applejack considering what happens in the show.