Louise Marie Auguste converted from the Evangelical faith to Russian Orthodoxy in St. Petersburg on 9 May 1793 (O.S.) = 20 May 1793 (.N.S.) , receiving the name Elizabeth Alexeyevna (Alexejevna, Alekseievna, Alekseyevna, Alexeievna, or Alexeevna).
She married Tsar Alexander I of Russia (Grand Duke at the time) on 28 Sep 1793 (O.S.) = 9 Oct 1793 (N.S.) in St. Petersburg at the Winter Palace, when she was fourteen years old and Alexander was seventeen. Alexander and Elizabeth had two children, Maria (1799 - 1800) and Elizabeth (or Elizaveta) (1806 - 1808). After the last child's (Elizabeth) death, Alexander pronounced that there couldn't be more children, because that was the will of god.
When Alexander took a mistress (Princess Maria Naryshkina) and had children, Elizabeth (Louise) also took a lover, Prince Adam Czartoryski (who was Alexander's friend). Later on in life Elizabeth and Alexander got closer together. She died almost a year later after Alexander's death.