What does Matilda Cook look like in the book Fever 1793?

Fever 1793 was written by Laurie Halse Anderson in the year 2000. The main character of the book, Matilda (or Mattie), finds herself caught up in an yellow fever epidemic that all but destroys Philadelphia in the summer of 1793. Mattie lives with her mother, her grandfather, and a hired cook named Eliza, and together they run a coffeehouse in Philadelphia.
We know that Mattie is a teenager of fourteen years of age, but there are few descriptions of her actual physical appearance. Instead, the novel chooses to focus on how the epidemic changes Mattie as a person.
At the beginning of the story, Mattie behaves as a typical teenager: more concerned with her own affairs than those of her family. She enjoys sleeping in, is content to let others do her chores, and isn't particularly physically strong. As she sets out to depart with her grandfather in one scene, we get some sense of Mattie's physicality:

"She looks like a china doll," observed Grandfather as we departed.
"I will break just as easily," I muttered.

Once the yellow fever outbreak is in full swing, Mattie herself falls ill but recovers fairly quickly. Mattie's mother then becomes seriously ill, so Mattie has no choice but to take on much more responsibility. This includes the harrowing task of having to inter her Grandfather's body once he dies from the fever. Mattie also decides to keep the coffeehouse open and asks Eliza to become her equal partner. By the end of the novel, Mattie is making very adult decisions. I would argue that her appearance is not nearly as important as the development and growth of her character.
https://www.scholastic.com/teachers/lesson-plans/teaching-content/fever-1793-discussion-guide/

There is very little physical description of Matilda (Mattie) Cook, but it is mentioned that she has brown eyes. She is said to have changed from a soft, young girl (page 43)—a typical teenager—to looking more like her mother by the end of the story. She is strong, both emotionally and physically, but I understand that she was a relatively small and thin young lady. Other than that, most of the descriptions of Matilda have more to do with her maturity than her physical appearance. Fever 1793 is the story of an ordinary teenager growing up in extraordinary times, having to grow up quickly and make hard choices. Matilda learns to be responsible and to survive in a city that is panicked and stricken by yellow fever, and this character development is shown more through her actions than through any physical changes.