I find physical descriptions of characters hard too. I tend to focus on a trait - in Eileen’s case, stubbornness - and find that a useful starting point. I also tend to hear voices, with images of what characters look like coming later. Does it matter? I don’t think so. As long as you’ve got a distinctive view of what your character is and how they’re likely to behave in any given situation, the rest will follow. Some authors prepare full bios for their characters. I don’t but there are no rights and wrongs here. It’s a question of finding the right method in character generation, the one that works for you.
Ensure dialogue is distinctive for your characters too. L’Evallier never contracts his speech whereas the Queen generally won’t but when under pressure the odd abbreviation will slip out. As for Eileen, her speech is as direct as she is. I can see the point of swearing to show a character under stress, to show their background, to show some of their attitudes but don’t like too much of the stuff. I treat swearing like paprika or chilli - only use a little.
To help make your characters seem more real you should have some reference to their family background. After all nobody comes from nowhere and while the family doesn’t have to appear in your short story or novel or whatever, it would be odd if your character doesn’t refer to them in some way, no matter how briefly. After all what you make the character says here can show a great deal of how they interact (or not) with their family and the reader can speculate as to how they’re likely to get on with people in general and whether they’re likeable or not. Also if the character gets on well with the family, do they do this to the exclusion of getting on with anybody else? Do they look down on others?