Forstner was born in Sigel Township, Brown County, Minnesota, on 3 May 1905, to parents Henry Boettger (1871–1943) and Caroline Tauer (1876–1955). She had 10 siblings: Viola (1899–1991), Walter (1901–1982), Eleanor (1907–1994), Caroline (1909–1980), Leona (1911–2000), Henry (1913–1987), Carl, Arnold (1916–1978), Harold and Leander.

On 1 February 1926, aged 20, she married Frank A. Forstner (1904–1975) at Holy Trinity Catholic Church in New Ulm. The couple had six children (four sons and two daughters): Eugene (1926–2001), Kenneth (1928–2016), Lois, Myron (1932–2022), Rollie, and Constance. The family farmed in Sigel Township.

Throughout her life, she experienced kidney stones, underwent a hysterectomy, and had surgeries to remove her gallbladder and cataracts. She was a member of the Cathedral of the Holy Trinity in New Ulm, and the Christian Mother’s Society. At the age of 110, she still received the daily paper, watched the Minnesota Twins on TV, and attended the church service at her nursing home every Sunday. At that time, her vision was good, but her hearing was not. Her daughter mentioned that she would never agree to use a hearing aid. When asked about the secret of her longevity, she replied, “I don’t know, I just live.” However, in another interview, she attributed it to getting plenty of sleep.

Veronica Forstner passed away in New Ulm, Minnesota, USA, on 29 September 2015, at the age of 110 years, 149 days. She was survived by five of her children, 39 grandchildren, 70 great-grandchildren, and 35 great-great-grandchildren.