Yes, after her role became superfluous, they couldn’t justify keeping her on the payroll, even though she was guaranteed (IIRC) only six or seven episodes out of every thirteen.
As another “featured player,” Nichelle Nichols had a similar deal, but fortunately turned out to be an essential part of the series.
I would never have guessed that by looking at her, but I wouldn’t have spurned her advances either. 
(Stolen from The Family Guy phone game) “As ship’s counselor, it is my job to write your college recommendation letter”
In actuality, George Takei and Nichelle Nichols were really good friends.
She stood up for Takei when he married Brad Altman.
~VOW
Nichell had a similar “casting couch” experience with a Desilu executive who was eventually fired for forcing himself on a number of women. She was also subjected to racial abuse by another (from Desilu or NBC, I don’t remember which) who apologized profusely when he realized what a shitheel he was. Nichell forgave him, showing again what a lovely person she was.
Being rotated around the ship, BTW, was not universally popular. When Riley was posted to the lower Engineering decks for his own protection in “The Conscience of the King,” he was sure he was being punished but couldn’t figure out why.
Agreed. While it’s true there’s things in TOS that haven’t aged well, it was pretty fair for it’s day.
Live-Action TV / Fair For Its Day - TV Tropes
Interestingly, the bad gets more obvious, while the good gets less. I recently read an article that mentioned Uhura taking over the helm and nobody reacted. No raised eyebrows or worried looks, nobody checking over her shoulder, just business as usual. Something like that wouldn’t even be noticed today but would have stood out in its time.
I think that was in “Balance of Terror,” after Stiles was ordered to the Phaser room. IIRC, she took over the Navigation station, so yes, she could fill in for another member of the crew when needed. She was able to control communications from the Navigation station as well.