"The first that died was sister Jane; In bed she moaning lay, Till God released her of her pain; And then she went away.
"So in the church-yard she was laid; And, when the grass was dry, Together round her grave we played, My brother John and I.
"And when the ground was white with snow, And I could run and slide, My brother John was forced to go, And he lies by her side."
This eight-year-old girl is certainly persistent. She is not going to give up in her quest to convince the speaker that she and her siblings total seven in all.
In these stanzas, she offers the speaker her siblings' names along with a few details. Her sister Jane died first, and then her brother John died. Jane died of a painful illness, and after her death, she and John played at her grave. And then in the winter, John died too. Note the seasons going by—each new season brings death.
Poor little cottage girl, she's had a tough life. She's experienced so many deaths at such a young age.
But we understand how she copes with death. She refuses to let go of her siblings, and they remain part of her daily life, even though they have been taken.
And let's note the girl's diction: Jane has been "released of her pain" by God; it sounds like she was suffering from a long illness. But, contrarily, John was "forced to go." It sounds like John's death was unexpected, or at least, not seen by the little girl as a release from suffering.
The little girl's siblings have died under different circumstances, so it sounds like she has a pretty broad understanding of death.