Question: What would be an appropriate title for an Emperor's mother who was not the wife of the former Emperor? The monarchy in this rather France-like fantasy empire is elected, and when a new ruler is chosen, the rest of his/her family acquire Imperial status as well. It is already determined that the ruler's siblings and children become Prince-Imperial X or Princess-Imperial Y, and their siblings' and childrens' spouses, as well as nieces and nephews, become Prince X or Princess Y, but what might the ruler's mother be called? Referring to her as the 'Dowager' something seems wrong to me, as she was never the wife of the former ruler, but I can't think of anything better, apart from also having her become Princess-Imperial so-and-so, but I'd kind of like something distinct from the other titles.
Searches: I thought Napoleon might be the best parallel, as an Emperor whose family did not previously hold titles, but apparently his mother was just called "Madame Mère de l'Empereur", which is... a bit dull ;) I also tried to find examples of Holy Roman Emperors who didn't inherit directly from their fathers, but in those cases that I could find, their mothers were already Duchesses, Princesses, etc. and I couldn't find any indication that they acquired a new title when their son became Emperor - please correct me if I'm wrong. I'm hoping that someone can think of a real-world parallel that I can borrow from, or failing that, make a clever suggestion to resolve this (really, really little) detail.