What I predicted below in page 1 of this thread is exactly what happened:
Sad to say, by real world standards what Burnham said to Spock was mild (and I'm not saying what she said was ok, but one need look no further than the news to see that real world discourse is far more cruel and brutal

)
The way the incident was presented before now was implied to be so horrifying that Burnham couldn't even tell Amanda. And they continued that thread with her reluctance to tell the Talosians, leading to anticipation of an act so horrifying that didn't remotely match what we actually got.
Plus, Burnham failing to tell Amanda let Amanda's imagination run wild to assume the worst, leading Amanda to shut Burnham out of the search for Spock. Honestly, Burnham should have said, "I called him a weird little half breed incapable of love," and Amanda would have said, "And...?" . Burnham: "That's it." After that, Amanda, while ticked off, probably would have let Burnham stay involved in the search. Unlike what actually happened.
And at least Burnham was sorry about it and apologized for it (and Spock knew that for some time since he told her "I'm not here to absolve you," right from the start). You're lucky if you get that in the real world these days. My own parents and brother have told me worse things than Burnham did and either refused to apologize for it or outright gaslighted me and said they didn't say it (either because they genuinely forgot or because verbal cruelty is just so common to them it runs together). Probably why at 35 years old my relationship with my parents isn't as solid as it could be.
The rumors are that Berg and Harberts were fired over verbal abuse to the Discovery writing staff, so I wouldn't be surprised if Discovery's writers themselves heard worse things said to them than what Burnham said to Spock.