Complex sentence: Lombard was returning from a successful War Bonds promotion tour in the Midwest, where she helped raise over US $2,000,000, making her the first female casualty of the US war effort in the Second World War.
Split into simpler sentences: Lombard was returning from a successful War Bonds promotion tour in the Midwest, where she helped raise over US $2,000,000. She would become the first female casualty of the US war effort in the Second World War.