She was born in Bridgeport, Connecticut, to her parents. Alexandra lived in nearby Darien until the age of 10 when she and her mother moved to California. They moved around for a year before settling in Mill Valley.
Her mother is of English and Irish descent. Alexandra’s half-uncle is NCIS (2003) actor Michael Weatherly. Her maternal grandmother Patricia Ruth Hetherington is Michael’s mother. She became interested in acting, photography, and singing at age 13. When Alexandra was 15, she moved with her mother back to Los Angeles to pursue her acting career.