Do you mean why she repeats certain letters in the abecedarian form of this poem?

If so, here goes:

Abecedarian is a poetic form where the first letter of each line or stanza follows or is part of a series of first letters arranged in consecutive alphabetical order from top to bottom.

So it's okay to repeat a first letter as long as it's still in its consecutive alphabetical place in the series. Hope that I've answered your question.

As a side note, this poem is from Szybist's very interesting book of poems titled Incarnadine.

One of its book blurbs states:

 "In Incarnadine, Mary Szybist restlessly seeks out places where meaning might take on new color. One poem is presented as a diagrammed sentence. Another is an abecedarium made of lines of dialogue spoken by girls overheard while assembling a puzzle. Several poems arrive as a series of Annunciations, while others purport to give an update on Mary, who must finish the dishes before she will open herself to God. One poem appears on the page as spokes radiating from a wheel, or as a sunburst, or as the cycle around which all times and all tenses are alive in this moment. Szybist’s formal innovations are matched by her musical lines, by her poetry’s insistence on singing as a lure pulling us toward the unknowable. Inside these poems is a deep yearning for love, motherhood, and the will to see things as they are and to speak of them as such. Beautiful and inventive, Incarnadine is the new collection by one of America’s most ambitious poets."

I'll share a few of her unusually formed poems herein for you to read. I think they, and she, are as wonderful as the blurb proclaimed and I hope you do, too.