I feel for Miya. She'd be a fine heroine in another manga, but she's totally outgunned by the competition here (mainly because Youichi is clearly into older girls). Maybe I'll go against the flow and root for her... heresy I know, but she's my type anyway (please don't become another kuro gyaru) and I love underdogs. I know full well she's practically fated to lose (no title heroine buff), but that never stopped me from supporting other losing heroines all these years.
Hana not winning would seem like a betrayal of the premise (that never ends well with fans) so I'm pretty sure she's the endgame here, not Miya. This manga just screams gyaru onee-san at every point, would the gyaru onee-san not win? If the mangaka wanted to torpedo his manga, maybe.
So Hana hates gyaruos. Did she or another gyaru she knew have a bad experience with them? Come to think of it, I've never really seen a "gyaruo" MC before, even in the spicy stuff where these guys tend to show up, they're always villains. Even in that reincarnation one, he's aware he's the villain and he's only the male lead as the twist of the premise.