I disagree with most of you. Infanta Cristina, as far as I know, was acquitted. An acquittal, in my books, means you should treat the person who got acquitted as if nothing ever happened. That's what acquittals are for. And if you now start to treat people acquitted (by a judge, who did his job) as if they were convicted you trample the very essence of what a judical system should be for. If that happens, why have democratic states with free, independent judical systems in the first place? If you ignore their verdicts anyway?
If it was up to me, Infanta Cristina would resume Royal duties, be present for family affairs, events abroad, etc. And yes, I would even restore her Ducal title.
EDIT: Infanta Cristina's husband, who was convicted, is another story, of course. He should stay in the shadows until he served his term.
best wishes Michiru