Davis was born in Mobile but grew up in Anniston, where her father had a medical practice. She was drawn to construction sites as a child to marvel at the process of building and always planned to become an architect. She graduated from Ward-Belmont School in Nashville, Tennessee and went on to enroll in the School of Architecture at Alabama Polytechnic Institute.
While a student she married one of her instructors, Charles F. Davis Jr. After graduating in 1935 they both joined the Birmingham firm of Miller, Martin and Lewis, Architects (she was paid $18 per week). She completed her registration from the Alabama Board of Architects on July 7, 1936. They worked there for three years and then moved to the firm of Van Keuren, Davis & Company (now known as Davis Architects), where he became a partner. In the 1960s she left the firm to open her own practice.
Davis was a deacon and elder at South Highland Presbyterian Church and taught the "Wannabees" Sunday School class for 10 years. When she died in 2008 she was survived by a brother and sister, two sons (Charles III and Neil), a daughter (Helen), one grandchild and four great-grandchildren. All three of her children pursued architectural careers.
Recognizing her long and pioneering career and contributions to the state, Alabama governor Bob Riley declared November 6, 2003 to be "Helen Sellers Davis Day". She was given a Lifetime Achievement Award by Auburn's College of Architecture, Design and Construction that same year.
- Carolyn Smith (1894-1987), believed to be the first female to practice architecture on her own in Alabama
- Sallie Smith, perhaps the first female to practice architecture professionally in Alabama
- Marguerite Spink, a female architect practicing with her father in the early 1900s.