I could see her hanging on to her hubby's corpse to allow her to travel freely around Spain . . . and perhaps the stories about opening the coffin to gaze on his decaying remains were just embroidery . . . or ugly rumors . . .
Some of her descendants were incredibly odd, though . . . but they were so inbred that they might have picked up the nuttiness from ANYbody, not necessarily Juana.
My daughter doesn't look very Latin, she's an Irish redhead through and through. I'm part Irish, so is her dad, and she got a double dose through the wonders of the genetic lottery. When she was living in Spain, people kept INSISTING that she MUST be Irish . . . she would say, "Well, actually, I'm an American" and people would respond, "NO! You can't POSSIBLY be! You MUST be Irish!"
Sounds like you’ve read some of the same stuff I have!
My personal contention is that she started out high-strung and flighty, then got a little unstable . . . but I don’t think she was clinically insane.
(But I’m playing her nutty as a fruitcake, ‘cause crazy is comedy gold.)