TheFork users who ate in Mandelieu-la-Napoule have said really good things about Le K, Le Chaophraya and Royal Mougins. Maybe you should give them a try!
Some of the more popular YUMS x2 restaurants that offer vegetarian options on their menu in Mandelieu-la-Napoule according to TheFork users include:
Le K, with a 8.7 rating
Le Chaophraya, with a 8.6 rating
Curry House, with a 8.8 rating