Sorry for the late comment, it turns out that Marie Brizard Essences Violette IS on Difford's Guide. The info even says that the violets are harvested in Toulouse to make the liqueur. Maybe you might know more about it than you think? Or was that MB's provided information? Eitherways, if I was in a better country, I'd have been more than happy to send you a sample of it for you to taste. I do find it kind of curious that there are so few MB reviews.
We have it as "Marie Brizard Violette Essence", so I stupidly missed it on my search. It's not a product I've ever tried or come across. The basic info we have for it was provided by a fellow Discerning Drinker who wanted to have it available for use in one of their cocktail recipes. Sadly, Marie Brizard have not engaged with us, hence the lack of their products and reviews on Difford's Guide.