Elizabeth is Schmidt's former girlfriend from college. She is portrayed by Merritt Wever.
Elizabeth and Schmidt dated for four years, and broke up due to Schmidt's change in behavior after his weight loss. Schmidt came to see her years later, wanting her to be his date to Cece's wedding. Initially she refuses, however later he comes to see her again with pizza, and to help him be nice again she tells him to eat the pizza. They then begin dating, although Schmidt is initially embarrassed about her being his girlfriend, but he decides he does like her.
She attends Cece's wedding with him, and everything goes well until Cece announces that she wants to be with someone else (namely Schmidt). Elizabeth believes he has feelings for his ex, and so she and Cece force him to choose which one of them he really wants. He runs away from the women, and we won't know until next season how this concludes. Long story short, he decides to date both girls at the same and time and soon regrets it when he gets caught and both girls break up with him.
Then, she comes back in season 5, and they reconnect. In the last episode show it shows them 5 years in the future, married with kids