Walsh was born in Seattle, Washington to a Brazilian mother and American father of Irish, German, and Swedish descent. She speaks fluent Portuguese and is proficient in Spanish. Walsh and her family moved to São Paulo, Brazil when she was two years old. At 11, she moved to Simi Valley, California to pursue her acting career. Walsh is a human rights activist, and spends much of her time volunteering and getting together community projects. She also enjoys travelling, reading, spending time outdoors, and studying psychology, biology, and neuroscience on her own time. Walsh also writes a personal blog on her official website.
In the fall of 2010, she guest-starred on CW's The Vampire Diaries as Sarah. In Atlanta, Walsh then filmed Mean Girls 2 as Mandi Weatherly, an A-list clique girl. Walsh was also on the Dr. Phil Show. In the segment she revealed painful memories from her time in primary school and gave advice to teens on how to best empower themselves. Later that day, Walsh shared some advice during a live webcast, sponsored by the Dr. Phil Show.
Walsh was the female lead in the TV series Zombieland as Wichita, taking over the role from Emma Stone. After filming the pilot episode, the series was not picked up. Walsh has had a recurring part since 2013 as Simone Sinclair, a former friend of Bay Kennish and friend / ex-girlfriend of Toby Kennish, in ABC's Switched at Birth. 
Walsh is an avid philanthropist, and spends much of her time volunteering and coordinating community projects,  ranging from supporting children with disabilities to writing a personal advice blog. In addition to philanthropy, Walsh also has personally written back to fans via her official Facebook page.