In real life, the series was concurrent with Trek, from 1966-68. Since this episode was aired on 10-28-66, Trek was already in production by a couple of months, so she may have taken off from Trek to run over to the filming locations of "Tarzan," since it was also on NBC. I wonder if it coincided with any of her absences on Trek?
Below, a rare candid photo of Nichelle after a guest appearance at an early 70's New York City Star Trek convention. We see Leonard Nimoy goofing around in a very familiar way with Nichelle, with writer Harlan Ellison in the background. (With tinted glasses and an arm around her waist.) Note the convention "Crew" badge worn by the lady on the left. It appears that Nichelle is in the middle of, or very close to, a "nip slip" in this photo! Copies of this photo are for sale on ebay, here.
Below, a rare publicity shot of Nichelle in character. I've never seen this particular one before now.
Below, a couple of montages of photos that were really too small to feature individually.
Bonus: Not a particularly rare image, but stunning nonetheless; Nichelle during the filming of (possibly) "The Wrath of Khan," or one of the other sequels, like "The Search For Spock". That mischievous smile is enchanting!