Tails.

Of Course.
Wouldn't you want a bit of revenge for people cutting of your tails?
Oh Dear.
Now a rainbow's tale isn't quite as nice
As the story we knew of sugar and spice
But a rainbow's easy once you get to know it
With the help of the magic of a pegasus device

Let's delve deeper into rainbow philosophy
Far beyond that of Cloudsdale's mythology
It's easy to misjudge that floating city
With it's alluring decor and social psychology
But with all great things comes a great responsibility
That of Cloudsdale's being weather stability
How, you ask, are they up to the task
To which the answer is in a simple facility

In the Rainbow Factory, where your fears and horrors come true
In the Rainbow Factory, where not a single soul gets through.

Maybe she's trying to make a rainbow of tails?
Yeah, that song is based of a fanfic called Rainbow factory, I Haven't read it though.