Charlotte is wearing different shoes with the white gown when they are walking through the park after the benefit than the ones she was wearing before the benefit in the car.
The story takes place in the autumn up to Christmas of the same year. Lisa's pregnancy doesn't show when she offers to help find a surgeon, but when the surgery takes place a few months later she appears ready to give birth.
No oncologist would ever use the word 'irradiation'. That is not a real word, and the correct term is Radiation Therapy.
The doctor said neuroblastoma is a soft tissue tumor. That is false. It is a tumor found in or on nerve cells.
Charlotte makes a hat specifically to wear to the ball, but she isn't wearing it when she finally gets there; presumably, she got distracted and forgot it.
When Charlotte is ice skating, Will says "The judges give it a 10! A perfect 10!" In the sport of figure skating, a perfect score is 6.0 - gymnastics is the sport where 10 is a perfect score.