What Mrs Holloway was doing was simple magic, she was making the gender, health, and maybe a bit of the willingness of the subject fit the cheerleader mold, but she wasn't forcing it on these kids. She was doing her best to make the team work with the people that had been selected, and that meant them being themselves. What she hadn't counted on was Trevor.
Trevor wasn't a Goth because it was cool, that's not why you did that, Trevor was a Goth because in the 8th grade he had a crush on Athena DeVires and this is where that path lead. He liked the people he hung out with, and it fit his personality, he was an introvert, and Goths tend to keep smaller social circles which tend to be closed off. But all of this sort of hung on that girl, at least for the first two years or so before it just sort of set in as a habit.
For Mrs. Holloway to change Trevor she would have to fix two things, gender and to make her an extrovert, you can't have girls leading cheers who don't like being around people. So she changed those things and created Trinity.
Trinity wasn't a goth who was there to chase a boy, she was a goth because she was pissed off at the world. She was much more willing to fight than trevor was, more willing to engage with the world around her, she wanted to spite the world and that's why she dressed like she did, why her hair was purple, she didn't give a fuck what people thought, she was driven by her passion. Goth was who she was, if you had a problem with that you could go fuck yourself. She was very pretty, and could have been a typical high school princess, but hated being talked down to, hated being treated like a babe, like a peice of meat, so she hid her beauty behind anger and strangness. In her heart she too just wanted to be left alone.