Say this happens in America.
The defendant files for habeas corpus.
"Here I am, Your Honor, filing for my own body to be produced for trial. Shall I leave and walk back in or will it suffice for your bailiff to say that I am in fact standing in front of you making this motion? Thank you."
From the article: In 2013, an Ohio judge ruled that Donald E Miller Jr would have to stay legally deceased, even though Miller was sitting in the courtroom to hear his fate, perfectly healthy. He had been declared dead in 1994.
A Jane Doe, who is also refusing to identify herself, by falsely giving the name of a dead person.
Just a guess, but imagine she would get jailed until someone can prove her identity. Which would be a long time.
Or she gets charged as a Jane Doe of sorts, with extra contempt stuff (do they have that in France?) heaped on for refusing to identify herself.
So just because they don't admit someone specific exists, doesn't mean they have to ignore that someone exists.
So does the administrative incompetance of both the government and legal systems.
The threat about driving is hilarious. So she drives, gets caught driving or speeding. Who are they then going to charge? Whatever answer you come up with, the response will be: But she's dead. Now what? They'll have to charge her. Won't that be hilarious: charging a dead person. For driving. Take that to court.
The seizure of assets thing. Linking the car as her asset has to be incompetant policing. The deceased estate has to close off sometime. So add that to the list as well.
In reality they know she's alive and they just don't want to fix it because they simply don't want to. The case where her identity was deemed dead just has to be overturned - the fact they won't implies they don't want to. Just because. More corruption.
What a mess.