The character of Kirsten seems inconsistent (spoilers)

She starts off being this nasty piece of work, easily manipulated, promiscuous and doesn't mind if people get brutally beaten up in front of her.

Then after a certain incident she goes through life with her self-worth destroyed, sad, mopey, a lost cause.

Then, twenty years later, with a little bit of a threat from the people trying to find her, she turns into Nikita and then The Terminator, slowly pacing a corridor with a shotgun, setting him and herself on fire.

It just somehow doesn't seem very emotionally honest - her character is basically twisted and manipulated to suit the needs of the story and script rather than have the story evolve around her character.

People may say "oh, but its when Tina is murdered that she decides to get vengeance and finds her confidence". But really? After twenty years of obsessing over her baby being murdered, she didn't decide ever to go after Ditlev or the others? Why not give another anonymous tip to the police, or the prosecuting lawyers, or just go to the police.

The murdered sibling's dad had been obsessed with the case for years, Kirsten must have known of him, why not contact him with some facts, pointers etc for his box of clues? Surely he'd have found something on her?

And if Ditlev etc were so keen to cover it up, murdering Tina, then why wouldn't they have somehow found a way of getting rid of the father, being that he's been snooping on the cast for twenty years?