You are right, anyone can write poetry and it doesn't even have to rhyme. That is where many people find it difficult to understand. You don't need to rhyme the last word in every pome. A simple way to write a poem is a limerick. This is only 5 line and follows an AABBA rhyming scheme. That means the first two sentences need to rhyme, the next two need to rhyme and the last one rhymes with the first two. Here is an example of how she can do this easily and make people laugh at the same time:
I once knew a man named Pat
He wore a big black hat
Until one day
The wind blew it away
And now he wears a rat
These types of poetry are simple, they tell a small story and they make people laugh.
There was an ugly old cat
He loved to spit and spat
He played in the road one day
Until a truck came his way
Now he is my new floor matt
It can be a lot of fun for her to write a few of these. I'm sure her teacher will love them and the kids in class will really laugh.