What makes a 65yr woman unable to sleep because of her sudden feeling of heat at night for a month?

Hot flashes. By sudden feelings of heat I assume you are experiencing something like hot flashes, which are a classic sign of menopause, which is common in women 62 and older (often usually starts before this age). The symptom is readily treatable with estrogen hormones (most common) and a few other atternatives. Certain medications could also cause similar symptoms.