> 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.

I don't really think that should be relevant to France's laws. Britain could after all change their laws.

But I do think this woman should be able to vote in these local elections as a legal resident. That should be the case regardless of citizenship. But it seems that would require changes to French law.