Horatia, gritted, and spat, and hissed, also show us the author standing by the characters, taking notes. Show, don't tell.
It's especially grinding when it's obvious that the character's words must be said in a certain way. If she says 'Piss off,' she's likely to be spitting.
From the mistress of many adverbs, J K Rowling:
'Gather round, gather round,' Hagrid encouraged.
This works like a tautology. You'd ne unlikely to say those words in any other way. 'Gather round', Hagrid screamed. 'Gather round,' Hagrid gritted. 'Gather round,' Hagrid snivelled...
So a new speech verb is only needed if there's a disconnection between what is said and tone of voice - if Hagrid, losing patience, actually HAD gritted. 'Gather round,' prior to draw a pistol and gunning them down. Otherwise Rowling is hitting me on the head with the bleeding obvious.
Even in the above case, it's telling, not showing. Better just to have him say 'gather round,' and have him move his hands in a wide welcoming arc - or draw his pistol, or fumble with it, or have the pov character notice his eyes narrow to dark slits.
Adverbs and specific speech verbs show a lack of trust in the reader. They weigh a text down. 'Said' was good enough for Hemingway, and Alan Garner doesn't even bother with 'said'. If we know the characters well enough, we shouldn't have any problem knowing who is speaking.