It's a pity that Universal didn't make a bit more of her. This is the only film that I have seen her in. I thought that she looked a bit like Tippi Hedren in some scenes.
She definitely offers a very striking image in the film. I also love her wardrobe and regal way/manner. However, one scene came out bizarrely funny to me in the film. When the villagers are extremely riled up in the tavern as Lionel Atwill is trying to settle them down with the doctor, telling them to seek out the monster to destroy him-she smilingly says with weird and misplaced upbeat glee "I'll take you to the ruins now". It just is such a wrong tone for the mood, troubled atmosphere and the link of the name Frankenstein to anything in that village with that crowd to say it that way.
Probably comes from shooting that scene in bits - the context may not have been clear. But I'm any case, Ilona is stunning. And I agree, her wardrobe is fantastic. I just read up on her on Wikipedia...she may not have had a huge movie career, but seems like she still enjoyed success as a singer and on the radio.