this poem depicts the innocent nature of a child who just does not want to understand that her siblings have passed away of natural causes and continuously reiterating her determined claim that they are still seven children.
That's a nice description of how the speaker (not Wordsworth) perceives the child. Like the speaker, you describe her response as refusing to acknowledge something patently obvious. Why do you think Wordsworth did that?
He prefaced Lyrical Ballads, which included this ballad, with a description of the wisdom of the rural people. Because they live close to nature, Wordsworth claimed, they'retheir perceptions are shaped by nature and its rhythms and processes. He believed they represent human nature is itself molded by the natural world. By contrast, educated urban residents are surrounded by an artificial environment and they have lost touch with the natural world and with natural human feelingsnature itself. By studying rural people and their feelings, he believed, we can find the natural feelings we have lost touch with. His poetry seeks to teach us how to find the human nature we have lost because of our artificial lives.
In that light, the child's insistence on including her dead siblings as continuing members of the family makes more sense. Death in nature is a seasonal affair, with flowers dying in Autumn only to reappear in Spring. Death is less an absolutethe actual end than part of something than a phase in a cyclical process. And the child knows this.
If you think about the poem as a commentary on the speaker, rather than the child, it is saying something about his limitations. Why is he so resistant to her perspective? Why so determined to teach her about his own, more artificial view of mortality as something final? Why can't he listen to this child of nature and learn from her about mortality in the natural world?
And why do we modern readers identify with that speaker and his blind ignorance of human nature? What does it suggest about us?
In reading Wordsworth's ballads, you need to reconsider things you take for granted before you can see that behind a simple story, like this one, lies a much deeper philosophical meaning. His poems often work in that fashion. But that's why they are worth reading over and over again.