That's a very dishonest and childish way to summarise the case. She is a legal long-term resident in an EU nation - France - having lived there for >15 years. However long-term residency status alone does not permit you to vote in local elections, you have to be a full-blown citizen. And given that you cannot vote in UK elections if you've lived abroad for more than fifteen years, she is now in a sort of limbo where she doesn't really have any local representation.

There are many stupid things regarding Brexit (primarily, that it took place at all) but this was a worthwhile thing to try to resolve even if it was a bit of a long shot.