"...acceptable to Queen Elizabeth?"

Are you kidding? "Acceptable" to a 91 year old lady/monarch who still won't give her son a chance to "reign" over whatever is left of UK if Scotland secedes? In asking her son Charles to live as she wishes him to live at 67, Elizabeth is one of the most respectively selfish mothers on the planet. 

And why would Callista be more "morally inappropriate" than Elizabeth's daughters in law? Or for that matter, Elizabeth' namesake, Elizabeth I,  who committed regicide, or her namesake's father, Henry VIII, a serial murderer?