Eeek! Explanations

One of the songs we like to sing is Miss Mary Mack which is also one of the clapping songs we used to play at school. The version we have on our cd finishes:

She went upstairs, stairs, stairs,
And bumped her head, head, head,
And now she's dead!

Alex has grown increasingly upset about some of the words - specifically "and now she's dead."
She asks:
Why is she dead?
But why?
But how did she die?
I don't want her to die.

And she won't take "I/We don't know - the song doesn't tell us." for an answer.