to help us laugh 

to help us understand her age

to help us think of bad things

to help us make our own list of fears

The speaker couldn't think of anything else to write

To make it rhyme

To make the poem scarier

To emphasize the speaker's point

The speaker is happy

The speaker is confident

The speaker is lonely

The speaker is worried

She is growing up and has different experiences

There may be a new kid at school

The other verses are very general experiences, this one is specific to being new to a school

None of the other things that were mentioned in stanzas 1-4 were really that scary

Maybe she isn't one of the "kissy little girls..."

Maybe they didn't say it very loudly

Maybe they didn't really mean it

Maybe they didn't want the teacher to hear it