Alexander began acting at the age of six, when she was cast in a Pittsburgh-area regional stage production of The Sound of Music as Gretl.

She worked professionally throughout her childhood at most of southwestern Pennsylvania's Equity theaters, including Pittsburgh Public Theater, where she won first place in their annual Shakespeare Monologue Competition for three consecutive years.

[3] In 2007, Alexander moved to New York City, and began doing commercial and episodic television work.

While still in high school, Alexander performed off-Broadway in There Are No More Big Secrets at Rattlestick Playwrights Theater.

Since then, she has worked on several television series, including Boardwalk Empire (2011), The Following (2015), The Sinner (2017), and Seven Seconds (2018).