Weirdly
I’ve had the “pleasure” living where I do if seeing her fan group a little
The bread and butter is genx and millennial moms and their children some of whom make that very young age group you mention
But she has a ton of 37-45 year old female fangirls
The foundation of Taylor Swift's fanbase has always been white Millennial women, whether they were in their teens during her "Speak Now" era or in their 30s for "Life of a Showgirl" today. And her lyrics have always reflected life at her age at the time (as well as the age of most of her fans).
She grew up and they grew up right alongside her with the same trials and tribulations. One reason she's enjoyed such loyalty and longevity.