As soon as I read your post, I thought about Frédéric Malle Iris Poudre. Très chic, in my opinion: it uses aldehydes in the opening (like No. 5) but they are much softer and the iris in its heart is just beautiful. I think it's in the same league as No. 5 but different enough to own both. Depending on where you are located, it may not be readily available to sample, though!
As a side note, there is no unsuitable fragrance for a 75 years old woman: my mum, who is 72, adopted Andy Tauer's L'Air du Désert Marocain as her signature perfume after sniffing it on me. And on her, it's much better than on me