To its credit, The Big Bang Theory has ensured it always includes nerds who aren't men, but really, Amy Farrah-Fowler and Lesley Winkle exist merely as female reflections of the boys. Ironically, the realest (and nerdiest) fangirl currently on TV isn't on TBBT at all -- she's a cartoon character.
Bobs Burgers' Tina Belcher is a true weirdo who shines a light on the strange, hormonally-charged fascinations of teen girl geeks. From her "erotic friend fiction" to fantasizing about kissing zombies, Tina unashamedly embraces all of the pleasures that nerdy girls are made to feel guilty about, as did Gravity Falls' boy band-obsessed, Mabel Pines.
The most underserved group when it comes to TV nerds is (as usual) the LGBTQ community; home to some of the most creative and passionate geeks of all. Queer, peppy heroines like Wynonna Earp's Waverley Earp and (until her unfortunate fridging) Supernatural's Charlie Bradbury fill this gap, and also provide a refreshingly gay twist on the Sexy Hacker Chick trope -- Felicity Smoak-types, whose "whole package" blend of tech-savvy hotness feels suspiciously like hetero-male wish fulfillment than they do an sort of genuine female empowerment.
TBBT has brought a lot of joy to a lot of people over the years, but as far as nerd representation goes, the show ranges from the two-dimensional to the grossly offensive. What was just about passable in 2007 began to look hopelessly past its sell-by-date as fast as the rate at which geek culture exploded into the mainstream a few years later. At their current rate of growth, it seems inevitable that the geek shall inherit the TV world -- just not wearing sweater vests or carrying restraining orders anymore.