Dieting help...........?

my mum went on a 1200 cal diet, and lost some weight from it but she cnt get dwn to her goal weight cos she says even when sticking to tht same amount of cals, the weight has jst stayed the same for a bit over a month now,,so wat does she have to do to shed those extra few kgs? she already excersises over 1 hour a day and consumes no mre than 1200 cals, would she have to reduce tht consumsion to further loose weight> like does ur body adjust to the amount of cals consumed to stp losing weight or smthing? thnks (: