There are a lot of clothing brands that exist, but the one for fangirls is definitely Her Universe. The company's face and creator is an entrepreneur by the name of Ashley Eckstein, who also voices Ahsoka Tano in "Star Wars the Clone Wars". She is an amazing businesswoman who created this amazing company to help give girls a chance to be as nerdy as the guys.
I actually came across this brand when shopping in the store BoxLunch, which is basically a more friendly version of Hot Topic. BoxLunch, as well as Hot Topic, has a deal with Her Universe and sells some of the apparel that is created by the brand in store. Ashley also has a deal with Disney, where she helps out with various videos, as well as designing clothes to be sold in Disney stores. All the clothing is designed with women and girls in mind. Therefore it is meant to be flattering, as well as represent your fan favorite obsessions.
The designs and clothing range from full out cosplay, to just supporting some of your favorite shows and movies. The first item I ever got from the brand was a "Wonder Woman" tank top, as pictured below. It was pretty much love at first sight.
The clothes are stylish, and not overwhelming in their design. I personally love Her Universe because it let's you let your inner nerd out without overdoing it, as well as having a reputable place to purchase items that will actually fit, and are what you ordered. Sometimes this can be hard when you purchase a fan shirt from a third party seller, and all of a sudden you have a poor quality shirt.
I have now added to my collection with the "Star Wars" Rey inspired cardigan. I love it because only fans will really see the pride you have for a fandom, but it's casual enough that I am happy to wear it any chance I get.
They are also known for showcasing up and coming designers in which Ashley hosts a fashion show. It's called The Her Universe Fashion Show. This allows young designers to showcase their inner nerd and talents, by creating outfits that go with a certain movie or TV show. One of the winners, Rose Ivy, had a design inspired by the popular TV show "Doctor Who". To all of those girls out there who have an inner nerd I highly recommend checking out the Her Universe website. They are an amazing brand that have styles that fit any personality, from the more reserved wanting to represent a series type, to the covered from head-to-toe in apparel type, they have it all.