What I meant about Kelly is physically and her outfit, not about how she behaves. A more fashioned girl, perhaps taller, more voluptuous or more fit, long stylished hair. It would have made her more mysterious when she started talking about her tragic life. I know this is a change impossible to do. However, my last critic of the game is that the girls' physical character design could have been better to fit their personality.
I'm Mexican, so I understand the difficulty of writing in a foreign language. I advice to get this app https://prowritingaid.com/
With it's rephrase feature (you write something and it rewrites it in 5 different styles you can choose), it will make your writing a lot faster and better. You won't have to worry never again about grammar and style, and you can even give each girl a style of talking. For example, Kelly using more slang, while the sister being more "refined" as she dreams of being a writer. It's not cheap, but it has saved me tons of hours of work and it was one of the best investments I've made.