I get what you're saying with Morwen being overstubborn (though this does not ruin her high position in my "opinion ranks"!
). And then, you could say that Nienor is partially responsible for her and Turin's suicidal end, because she was stubborn enough not to go back to Doriath.
A thought invaded to my mind a short while ago. It is quite ironical (yes, more of that) that Hurin's kin do almost as much, if not as much, damage in a lifetime than the Doom of the Noldor in a couple hundred years. Nargothrond fell when all of them (except for Lalaith, of course) were still alive. And shortly after their end - Doriath, followed by Gondolin. All of these losses were caused directly in Nargothrond's case and indirectly for the other two by the Curse, or by the actions of the family (if you prefer it that way).
But the
good thing about it is that Morgoth's Curse, like all his other deeds, ultimately turned against him. If it wasn't for the sac of Doriath and Gondolin, Earendil and Elwing would never have met! And then Earendil would never have gotten the Silmaril that helped him get to Aman. So Morgoth created the perfect circumstances for his own destruction.
ETA: I forgot to say this. "Fixed idea" - I think tht this could be said about many characters from the Narn. And it does relate to stubborness. But sometimes you can't tell one from the other. For example, when Morwen against all councel leaves Doriath to look for Turin, I think it's more of a fixed idea than simply "pig-headed-ness".