From what I understand she didn't 'qualify' for full Queenship because she'd been married before, but Charles insisted that she be given the full title of Queen. Since the Royal Brits have rules and rules on top of rules, she had to be annointed just like Charles was, and he saw to it that it happened.
As an aside, I think the whole muddle is Camilla's fault. Back in the day, she didn't want to wait for Charles to complete his training - like Catherine did for William (remember how the press called Catherine 'waitee Katie'?)
Camilla was impatient and got married, but she and Charles never broke up... as Diana said, there were three of them in the marriage. Camilla got divorced before Diana died (waiting in the wings?) and it was just a matter of time before she and Charles would hook up. In a way it's a good thing Charles originally married Diana and not Camilla - I can't imagine what their 'issue' would have looked like.
So Charles finally has the woman of his dreams and some day William will sit on the throne. At least Harry was smart enough to ditch the lot and get the hell away from that disfunctional family.
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