During her first year of veterinary school, Dr. O'Brien developed an interest in cancer research and treatment after her own cat succumbed to lymphoma. She earned her DVM from Kansas State University in 2008, where she received an award for proficiency in oncology. The following year, she undertook an internship in small animal medicine and surgery with VCA San Francisco Veterinary Specialists. In 2012, she completed a three-year residency in small animal medical oncology at UC Davis and obtained board certification. She stayed on an additional year at UC Davis as a clinical staff oncologist. She authored the largest collective study on canine splenic marginal zone lymphoma, and has further research and clinical interests in canine melanoma and feline and indolent lymphomas. She also enjoys collaborating with other oncologists in conducting clinical trials. Dr. O'Brien's top priority is to help all her patients achieve a better quality of life, regardless of their circumstances.

In her spare time, Dr. O'Brien enjoys visiting her local cat shelter where she can give love and attention to cats who have not yet found a home. She also enjoys running, yoga, painting, spending time with her husband and spoiling her own cats, Cloë and Jaxon.