The idea of her turning into her dad is fine... lay the ground work for god sake, not an arc from sane sensible character to mad queen in the space of 30 minutes in the FINAL season when little has been developed in 7 seasons or some 70+ hours of TV show..

Exactly. I have no problem with her being a flawed, tragic character if it's done well. People are saying "remember way back in Season 2-3 when she crucified some innocent-ish Great Masters with no trial against the advice of Barristan Selmy?"

Actually, I have to answer "No, I barely remember that" because it was so long ago. But after rewatching it, sure, she's made some mistakes.

The problem is that she's gradually gotten better. So her arc is that she starts out young, impulsive, and wrathful. Then she gradually becomes more reasonable. And now she's going to have a downfall over the course of three episodes?

Her descent into madness is something that should've taken place over 30+ episodes.