We are 4 cousins, and our aunt gave us the bare ownership of one of her apartments while retaining the usufruct. We all want to sell it, but she is against it. Can we get legal permission to sell it?

No. When the ownership of an asset is dismembered, i.e., divided between a bare owner and a usufructuary, in principle the judge cannot authorize the sale of the asset against the will of the usufructuary (art. 815 -5 C. civ.).