She is not used to eating heavy supper in the evening这句话正确吗?

1.有错,需要在eating和heavy中间加入a.
2.breakfast/lunch/supper前面一般没有冠词,但是如果有其他形容词修饰时,这时一般需要加上不定冠词a/an.
如：have lunch 吃午饭 → have a light lunch 吃一顿轻便的午餐 → eat a heavy supper 吃一顿丰盛的晚饭