yes we've seen her burn people, ,most of who deserved it, yes she's talked shit about burning cities down, yes she lost a lot in a condensed period of time, yes she has an attention whore complex, but we also have seen for 8 seasons that she's not a monster. that she has a 'gentle heart' at times, that she really did feel so horribly that when her dragons burned a baby, she locked them up, etc..

her going at the red keep and burning every woman and child around it alive would make sense. her burning the city down if cersei had fled and she was obsessed over killing her no matter the cost would make sense, her going ham after drogon got hit in the tail (of if they clipped Rheagal in this ep instead) would make sense.

her going block by block committing mass genocide because idk she crazy, not so much. this needed more runway.