It's not teenage girls though. The most obsessed swifties are usually in the 20-30 range, people who literally grew up with her and her apparent lifestyle and music changes. Teenage girls do listen to Taylor Swift, but your average teenage girl is just as likely to be into Billie Eilish or Ariana Grande or any K-pop. The people who get para-social with it (to name a couple of real-ass examples, getting tattoos of her handwriting or theming rooms around different albums) are the people who have been celebrity gossip column following her for years, and trying to convince their friends that in fact she personally writes all of her tweets well into their 20's.

Her music is whatever, what bothers me is how deeply they've fallen for the marketing schtick.

Edit: More specifically, it is their tendency to think that if you don't fall for the marketing schtick, that makes you a 'bad person who is just jealous of her success'.

I think for a few celebrities- Beyonce, Nicki Minaj, Taylor Swift, Elon Musk, Jordan Peterson- there's a point where it becomes a whole new level of parasocial relationship. The line between toxic fandom and cult is pretty blurry. The hosting website also has a bunch of hentai and shit so NSFW but that episode of QAA has some pretty extreme fans using biblical gematria to prove that Taylor Swift is secretly gay: https://kemono.su/patreon/user/12883973/post/93239821

Except she's been around for 10 years and we have watched them very obviously not grow out of it.

thats sort of the weird part, its been going on for 10 years and people only get more obsessed.

The weird part are those who don't grow our of it.