Yes, I agree that it is likely Jeanne in the new joint photo in national costumes. I also agree that it says “J. Calment” on the back, rather than “G. Calment”, as Nikolai Zak thinks. I was just debating this point with him on Facebook a few days ago — ironically, using nearly identical arguments as you stated:

I can also see similarities between other photos of Jeanne and the lady in the costume:

However, to your point about there being no wake — there actually was, as pointed out here on page 7:

Débat sur l'authenticité de l'âge de Jeanne Calment - Page 7

Here is the announcement: