Conversation so far:
What was the second marriage of Wallis Simpson?
Wallis had become involved with Ernest Aldrich Simpson. He divorced his first wife, Dorothea, to marry Wallis on 21 July 1928.
How did Wallis Simpson meet her second husband?
By the time her marriage to Spencer was dissolved, Wallis had become involved with Ernest Aldrich Simpson.
Did Wallis Simpson's second marriage last?
Wallis filed for divorce from her second husband.

Question: When did she get divorced?
Self-contained rewrite: When did Wallis Simpson get divorced from her second husband?