Conversation so far:
What was the second marriage?
By the time her marriage to Spencer was dissolved, Wallis had become involved with Ernest Aldrich Simpson, an Anglo-American shipping executive and former officer in the Coldstream Guards.
How did she meet him?
He divorced his first wife, Dorothea (by whom he had a daughter, Audrey), to marry Wallis on 21 July 1928 at the Register Office in Chelsea, London.
Did the second marriage last?
CANNOTANSWER.
When did she get divorced?
CANNOTANSWER.
Can you give me any interesting information?
The Simpsons temporarily set up home in a furnished house with four servants in Mayfair.
Did they stay in Mayfair?
In 1929, Wallis sailed back to the United States to visit her sick mother.

Question: What happened to her sick mother?
Self-contained rewrite: What happened to Wallis Simpson's sick mother?