The sweater is from Urban Outfitters
Unfortunately, they are all sold out of that exact design online but they have a few left of a different design for $9.99
It might still be available at local stores, so you can always check there.
Here are a few other options from Urban’s online site:
I did a quick search and couldn’t find anything that mentioned the exact brand she wore. My guess is that it was Madewell or ModCloth but there’s a possibility that it was custom-made. Quite a few articles of clothing on the show are custom-made.