She has a couple of different reactions worth noting. On pages 41-42, we see these. She first reacts by questioning if he is drunk. He makes more noise than usual and she wonders what the deal is. He is a little forceful about having the light on and won't just comply with her request.
Later, she actually touches him and finds that he is wet from sweating. The sad part of this entire section is that Mildred reacts to Montag's sickness by putting her seashells back in her ears and moving on with her sleep. A true loving wife would probably take care to help manage her husband's comfort. She gives not one ounce of care.
She is actually quite suprised becuase he is never sicks. He ask for aspirin and water beacuase he feels bad. The reason that he feels bad is becuase that they the firemen had burned an old lady to death. They id not mean to do this but the woman lit the match igniting the kerosene. This killed the woman fairly wuickly as her house and body went up into flames.
Hope this helps :]