This War Bond Rally radio spot from August 20, 1947 (possibly earlier as the war was over in 1945) on the show Guest Star features Mary Small and Jimmy Stewart. In the first part of the recording posted here Mary sings. In part two, included in the following post, Mary interacts with Jimmy Stewart, pretending to be his biggest love-struck fan.
More examples of her patriotic duties and charitable efforts during WWII and afterward are spread throughout this blog. I discovered this recording thanks to Jerry Haendiges at the Vintage Radio Place found @ http://www.otrsite.com/.