Christie is not a vegetarian. True that she eats a mostly vegan diet but she does eat oysters so that does not qualify as a vegetarian. Here are a couple snippets to back my conclusion:

"However, Ms Brinkley, who launches her eight-product Christie Brinkley Authentic Skincare line today on HSN, admits that while she is almost entirely vegan these days, 'Life is too short to not have oysters and champagne sometimes'

And also this:
'Now, though, since Fukushima and BP in the Gulf, I don't eat fish apart from the occasional oyster,' she says, in reference to the 2011 Japanese nuclear power disaster and BP's 2010 oil spill in the Gulf of Mexico respectively.

You can find the article here:
www.dailymail.co.uk/femail/article-2986800/Supermodel-Christie-Brinkley-61-claims-ageless-appearance-result-lifelong-vegan-diet-admits-cheats-oysters.html