I do not think it is a WWI Army Nurses uniform. My grandmother's Uniform was quite different with a coat and belt. It was donated to the Historical Society of the Western Reserve (Cleveland, Ohio). They were excited to get it as they are very rare.

She was a Commission Officer. I can find no records of WWI female Officers. I was even told at a WWII WAC Museum that they did not exist. Yet we had the medals and documentation that was donated all together. We still have a letter from the Queen of England thanking the US Army Nurses for all of their support during the Great War and photos of her helping patients.

It could be a Red Cross Uniform, as the joke was that she thought she was joining the Red Cross because they had the nifty cape and she ended up with the big frumpy coat and belt.

Good Luck on you search.

Jill