Joy Divison wrote...
Yes it does make you wrong. Saying "she acted like it never posed a threat" is patently false. You might feel she underestimated the threat, but that is not the same thing. Saying "she was so confident she could handle anything thrown at her" is also wrong, she comes out and flatly admits it when she asks Hawke to accompany her to Sundermont.
It is possible to interpret her as overly-idealistic, obdurate, ill-conceived, or borderline reckless but you are contending something entirely different that is unequivocally refuted by in game evidence.
Merrill's sin is pride. She is sure that she can restore the mirror. She's positive that she can protect herself from the demons, even when making a deal with one. She doesn't listen to others, so sure is she that she's right. Even when asking Hawk for help, one gets the impression that she's going against her better judgement to do so.
That's why the Pride Demons are able to get her time and again.
And honestly, Merrill, cute as she could be is exactly what I don't want in DA 3 in terms of companion relationships. With her so many of the options ended up comming across as enabling bad behavior. Killing some blood mages while enabling others just felt wrong to me. I wanted to be able to be more consistant. To express my agreement with Merrill's goals while not accepting her means to those ends in no uncertain terms.