which word in the simple subject of the sentence my best friend wrote a funny poem about her pet rabbit

my best wrote a poem about her pet rabbit

The rabbit was her best friend and she loved it and took care of it.

That is the 1 paragraph or intro

In the sentence:

My best friend wrote a funny poem about her pet rabbit.

The simple subject is 'friend'. Remember that a simple subject is the main word or words in a subject, so it does not include any of the modifiers that might describe, characterize or restrict the subject (in this case, the possesive 'my' and the adjective 'best')