"Their graves are green, they may be seen," The little Maid replied, "Twelve steps or more from my mother's door, And they are side by side.
"My stockings there I often knit, My kerchief there I hem; And there upon the ground I sit, And sing a song to them.
"And often after sun-set, Sir, When it is light and fair, I take my little porringer, And eat my supper there.
These lines are one big quote from the little girl. She understands the speaker's point of view, but by golly she's gonna try to explain her thinking and, in doing so, try to change the man's mind.
She explains how her dead siblings are part of her daily life. They are only "twelve steps" from where she lives with her mom, and they are laid "side by side" Even in death, the siblings are physically close (a whole lot closer, we might add, than those living siblings in Conway or the ones who are out to sea).
The little girl adds more: she hangs out at her dead siblings' grave sites regularly. (Creepy or sweet? We'll leave this one up to you.) And their graves are green. Green, of course, is the symbol of nature and springtime and life. (We're looking at you, Gatsby's green light.)
So, she chills at their graves, knitting stockings, hemming handkerchiefs, eating supper out of her "porringer" (a shallow bowl). She even sings songs to her dead sis and bro.
Even though the little girl's investment in her dead siblings is one-sided (there are no ghosts or zombies in this poem, we're sorry to say), they are still very much part of her life. They may be gone, but the little girl visits their memory daily by spending a whole lot of time at their graves. They may be dead, but they are very present in her life.