She plays Alvin's daughter, Rose, as a deeply sympathetic woman who is a little slow on the uptake, but is devoted to her father. Rose has a speech impediment, but Spacek manages to put Rose's difficulty communicating to great comic effect. Rose knows that her father's stubbornness is why he has survived as well as he has, so she is resigned to it, but she is also of the opinion that this same stubbornness will get him into trouble, and she is worried that someday she won't be able to get him out of it. She is almost beatifically fatalistic, keeping her ambitions small but determined to achieve them, refusing to give in, whatever her own limitations. Like father, like daughter.
Family is family.