What to do if my 77 year old grandmother is having severe constipation , even anema hasn't worked?

Go see Gastroenterol: Assuming that she's tried to maximize fiber, fluids & exercise, then she can consider over-the-counter stool softeners & laxatives. Failing that, take her to see her Family Doc or Geriatrician to review medications for causes & check for hypothyroidism, anemia etc. After that, need to go to Gastroenterologist for colonoscopy.