Your mother is suffering from postmenopausal bleeding (as last bleeding was 1.5 yrs ago).Sonography
report shows bulky uterus with endometrial thickness of 14mm. It is called endometrial hyperplasia
and leading to future risk of endometrial carcinoma
Normal endometrial thickness in postmenopausal age gr is less than 3 mm.
So need to undergo endometrial biopsy
for histopathological examination and rule out carcinoma if any. Consult with your gynecologist and take T/t accordingly.