Snow was born and grew up in Tampa, Florida. She is the daughter of Cynthia, who works for Prentice Hall, and John Snow, Sr, who ran an insurance agency until retiring to organize Snow's schedule. Brittany has one half-brother, John Jr., and a half-sister; both of them live in Ohio. She is a good friend of Bethany Joy Galeotti, Sophia Bush, Amanda Bynes, Zac Efron and Arielle Kebbel. Brittany attended Carrollwood Day School in Tampa, Florida, for her early education (kindergarten through second grade). For middle school, she attended Ben Hill. Brittany is a 2004 graduate of Gaither High School in Tampa, Florida. She enjoys spending time with friends and family, often visiting her hometown of Tampa, Florida. Snow is Catholic.

Brittany has also recently revealed that she struggled with anorexia nervosa during her teenage years. She has since then joined various causes to promote and try to help other youth struggling with this issue.