I think it's probably true about the overshadowing. Irene was pretty but in a quiet, plainer way than Alix & Ella who were dazzling. Plus, she lacked VMH's forceful personality so she kind of ended up in 4th place. Then you look at the family connection--the Henrys were certainly popular w/their relatives for visits, official occasions, etc...but didn't do anything spectacular to warrant non-royalphile interest nowadays. She wasn't the mother of Earl Mountbatten or Queen of Sweden or grandmother of Prince Philip; she wasn't a legendarily beautiful GDSs who became a nun then a saint; she wasn't the tragic, beautiful last Empress of Russia w/all the accompanying drama of hemophilia, Rasputin, Revolution and horrific death. Irene just led her life quietly, suffering to be sure the tragedies of her family, but passed on just as quietly and out of public notice.