I'm not sure if I should tell this story or not. On the one hand, it's nobody's business. On the other hand, Grace Lee Whitney was a good person with a hard life, and this is a good illustration.
I never met Grace Lee Whitney, but I was friends with one of her old boyfriends from the '60s, and someone who worked on TOS. I'm not going to name my (living) source because they'd take flack and they're old and don't need this crap, so if you want to say I'm lying, that's cool. Anyway I was told why she got fired midway through the first season. There were basically two reasons.