I like how the manga shows us the Silver Millennium times with Nehelenias memories but to be honest it tells us more about Queen Serenity and princess' birth celebration rather than about Nehelenia herself. The Dead Moon Queen remains pretty regular big enemy in the manga, obsessed with Silver Crystal and all. Thats why i like the 90s anime Nehelenia more. She's so much more interesting and her backstory is really creepy and sad if you think about it. I also like how emotional she is. It was a nice change after all big bosses in the manga and anime (Metalia, Death Phatom, Pharaoh 90) were rather cold monstrosities
Wouldnt mind if the movies expanded on Nehelania memories in Silver Millenium, even if just a bit