How can i get her to understand ?

My mother is angry with me because my grandfather ( her father ) has been helping me financially I'm only 18 I live on my own with my son and I do work he just helps me with child care , gas etc. Because he knows that I do need a little help every once in a while and I'm very grateful for it she's mad because she says that she's his daughter and she's struggling but he won't help her anymore. Although he has helped her most of her adult life she just took advantage of it I'm not sure how to get her to understand that he's really only helping me because I'm a young single mom I'm trying my best she does not try to even work so he stopped helping her.