In "Rikki-Tikki-Tavi," what does Nagaina do alone to try and complete her and Nag's original plan?

In “Rikki-Tikki-Tavi,” Nag and Nagaina are a married pair of cobras living in the garden of an English family in India. They want to get rid of the English family because they believe that, if they do so, Rikki-Tikki-Tavi, who is a mongoose that lives with the family, will leave the area. They know that mongoose and snakes are enemies and they believe that the presence of Rikki-Tikki will be dangerous for them.
In order to get rid of the family, the two snakes plan that Nag will kill them. He will start by killing the father when he comes for his morning shower. Then he will kill the others.  Nag says,

I will kill the big man and his wife, and the child if I can, and come away quietly. Then the bungalow will be empty, and Rikki-tikki will go.

This is their original plan. However, Rikki-Tikki hears of it and ends up killing Nag. This means that Nagaina is left to carry out the plan on her own. The next morning, she goes to where the family will eat breakfast and waits there.  When Rikki-Tikki gets there,

Nagaina was coiled up on the matting by Teddy's chair, within easy striking-distance of Teddy's bare leg, and she was swaying to and fro singing a song of triumph.

Teddy is the child of the family. Nagaina has come to kill him and then kill the rest of the family. This is how she plans to complete her and Nag’s original plan.
http://www.cs.cmu.edu/~mongoose/rtt.html