Thank you Lady Finn for the link. I swear Mette-Marit curtsies at the drop of a hat! No wonder she does them so well. She has plenty of practice!
I genuinely believe this to be a case of either a mistake in protocol or a personal reverence, not a protocol one.
Protocol is protocol. A prince should bow to his king at any age. Being a Crown Princess by birth has no more seniority than being a Crown Princess by marriage in international protocol. Consorts are afforded the same courtesies as one born in the position. Mette-Marit just curtsies to everyone! She curtsied to Camilla, who also married into the position, even though Mette-Marit had been married longer!
I'm not suprised by hearing that Diana curtsied to King Constantine. The BRF are relatives of the GRF and still acknowlege their full titles as was evidenced
by the scandal at the wedding of Charles and Diana. Other houses, such as Norway, do not recognized the HM and HRH styles of the GRF so it would be interesting to see if they bow and curtsy to the GRF members (except Mette-Marit of course, I'm sure she curtsies to them too!
).
I have been looking around this afternoon and have yet to find a picture of Marie-Chantal curtsying to anyone that wasn't a monarch, but I'll keep looking. I would be suprised if she did.