The actress will portray a character named Mimi-Rose Howard, debuting in the fifth episode of the season, appropriately entitled "Mimi Rose". A representative for HBO would only confirm that Gillian Jacobs will appear in Season 4, but it isn't known how many episodes she is slated to appear in.
Vulture reports that, just a few months back, Gillian Jacobs starred in a short film alongside Jack Antonoff, the boyfriend of Girls creator Lena Dunham. The short was created for Jack Antonoff's sister's spring 2014 clothing line, CRUSH.
Season 4 of Girls is slated to debut in early 2015, although a premiere date has not been given yet. Gillian Jacobs, who played Britta Perry for all five seasons on Community, recently starred in Walk of Shame and she will next be seen in Life Partners and Hot Tub Time Machine 2 on the big screen.