“8 degrees above 30” is a weird way to put it. Is that normal Japanese terminology for talking about a fever? Normal human temperature in Celsius is 37 (give or take a fraction), so what she has is a fever of about 1 degree (less than 2 in Fahrenheit, where her temperature is about 100.5), and that’s not “a high fever”, certainly not something that would make you collapse or make a doctor expect that you were about to drop dead. (Although it would be enough to send you home from school/work.)