The woman answers with a soft voice that shows she's almost on the edge of tears. "She took sick quickly two days ago. I thought it was just some simple sickness that bed and good meals would fix, but she's just gotten worse. She complains of chills, and has had a fever for the last day. She cannot keep any food down now, and is too weak to leave the bed. It got worse so quickly, she's been sleeping fitfully for the last few hours, but every now and then she cries out in her sleep as if in pain."
The girl has a fever, and a fairly severe one. You do not see any rashes or physically manifesting symptoms besides the fever, and flushing in the cheeks. Her cheeks are slightly sunken in, like a child that hasn't eaten well in some time, but the way her parents look, you doubt they are desperate for food, even with six children, so the sunken cheeks are likely a symptom of the illness.