A poet's word choice can be based on many different things. Many times, a poet examines the intended audience and chooses words based upon their knowledge of terminology. Other times, a poet will chose to write according to the times (period for which they are writing) or even the mood. That being said, one cannot state that all poets use the reader as the main reasoning behind word choice.
One could assume that Andrea Hollander Budy choose to write in a specific way given her poem contains the same title as the story tale "Snow White" and, therefore, appeals to children. her word choice, for the poem, is not very elevated. Instead, her word choices are elementary and basic.
The poem offers a very different perspective on why Snow White decided to stay with the dwarfs in the woods. Instead of the historically accepted reason (hiding from the Queen), Snow White id stated to have made the decision to stay with the dwarfs because Bashful kissed her.
That being said, the poem is not specifically written for children. Instead, it seems to speak to women, who have had children, who wish to be saved from "the plainness of your life."
Regardless, the words chosen mirror the children's tale. It is relatively simplistic and easy to read. The words do not need defining or explanation. In the end, one can really only assume as to why a poet chooses one word over another.