I remember hearing something about things that never stop growing, they just slow down... like your nose and ears... that's why you see so many old guys with huge noses and ears (the womens ears are probabily bigger too, they just cover them with hair)
It could also have something to do with their hormones changing (estrogen levels dropping as they near menopause)
You could also just be paying more attention to their nose because maybe your not distracted by other parts of their look (maybe they wear less crazy makeup/jewelry/clothing/hairstyle... you're no longer distracted by all the other stuff)
It is because your skull keeps growing even after you stop growing. I think... But I am not sure.
I also noticed, ears get bigger too and this happens in men too, not just women.