Mesley's statement is confusing with regards to exactly what she said in this situation.
https://twitter.com/user/status/1276263794684186625
She mentions the incident last fall where she said the title of the book in a meeting. It doesn't appear she faced any discipline over that, she just had a colleague tell her it made people uncomfortable.
In the incident where she was disciplined, it sounds like she was quoting someone who was quoting someone else who used the actual n-word, but the person she was quoting directly only used the euphemism "the n-word". So, instead of quoting the person as having said "the n-word", she said the actual slur.
It seems like she's doing the classic spin doctor move, when you do something indefensible (casually say the n-word in a meeting), bring up another incident where you did something similar but easier to defend (saying the n-word in a meeting while quoting the title of a book) and then link those events in people's minds. Then, proceed to talk in detail about the easier to defend incident while being less-detailed about the harder to defend one. She uses 6 lines of text when referring to the incident that actually led to discipline and uses vague language that makes it hard to tell exactly what was said. She uses 14 lines of text and is very detailed when referring to the other incident.
I'm not sure if she intentionally did that to spin public opinion in her favour, but as someone who was on Marketplace for many years, it's a technique she should be very familiar with.