I focus on personality traits. In Eileen’s case I knew she’d be as awkward as they come, often to her own detriment, but she would also be brave, honourable and prepared to make considerable sacrifices for causes she considers worthy enough. So being prepared to give up what the Queen considered a privileged lifestyle for a much more humble life on Earth with a mere human male is something someone like Eileen would do without that many qualms. I have since fleshed Eileen out physically with chestnut hair, a good figure and great skin. But I do think the physical attributes are less important (though Eileen has been known to use her physical wiles to help her cause, especially when she was living in the Kingdom). Had I been stuck for physical attributes, one good idea often repeated in writing circles is to take photos from magazines and so on and “blend” different features from pictures you like to create your heroine. I’ve found it helpful to “see” my heroine in action, doing things, speaking (and getting a good idea of her voice did help give me her class and as a result ideas as to what she’d look like – she’d be unlikely to be a blonde bimbo) and from that other aspects of Eileen’s life, including her looks, fall into place.
Other Favourite Feisty Characters?
A very early favourite of mine has always been Jo from Little Women. I always liked the idea of her writing as her way of doing something positive with her talents. Hermoine Granger from the Harry Potter series shows courage and determination, traits I like in any character. I've never had much time for pretty and useless "heroines" who are only there for the hero to rescue. I like my ladies (of all ages) to be able to do something practical to help themselves even if that ideas fails. There's no way either Jo or Hermoine would waste time screaming for help. They'd be far too busy trying to get out of whatever scrape they'd got into. Elizabeth Bennett from Pride and Prejudice is another good example.