Somehow these were overlooked in previous research.

1) A long profile by Ira Wolfert that ran in the Milwaukee Journal, October 12, 1940, headlined "Singing Elsie Houston of Historic Family Tells of Voodoo Dangers." It is very much a personality profile, focusing on EH's experiences with precognition and mind reading, and her mounting frustration as a telephone keeps interrupting the interview.  Rather than excerpting it here, I'll send you directly to the article. 

2) A March 4, 1942 wire story, run in the (Regina, Saskatchewan) Leader-Post, that frames her Town Hall solo concert as a classic understudy-becomes-a-star story (she had replaced Grace Moore at the last moment). "The critics gave her rave notices. She is swamped with offers. And that's how a prima donna is born."

3) A concert note in the August 18, 1942 (Baltimore, MD) Afro American that briefly describes a Boston performance at the Satire Room of the Hotel Fensgate. Of particular note: Elsie Houston's description as "colored Brazilian soprano," a rare explicitly racial reference to EH.