she didn't suddenly flip and again, apply your logic to the red wedding to realize how faulty it is.
The show needed more time for Dani and Jon's relationship, yes absolutely. The show did not need more time for dani descent because that defeats the point of it. If melting surrendered soldiers isn't enough for you, nothing is going to be You are supposed to be shocked, then piece together the clues. But because it happened in the show before the books the insuferrables are going to be insufferable.
She didn't melt surrendered soldiers, she executed a pair of traitors who explicitly refused any punishment but death. She did exactly what literally every lord in Westeros would have done in that situation but somehow she's mad for it. And let's not waste time claiming they weren't traitors, because they swore loyalty to the usurper who killed their rightful queen and betrayed their liege lady. Meanwhile Tywin seals an entire house in mines and floods them because they disrespected his father, but nbd, he's totally sane. Stannis executes many people by burning them alive, but he's not mad either.