It isn’t even hers but came to her in the rain or the soft wind,
which is a gate through which her life keeps walking.

She can’t see
herself apart from the rest of the world
or the world from what she must do
every spring.
Crawling up the high hill,
luminous under the sand that has packed against her skin,
she doesn’t dream

Based on what is happening in this part of the poem, the repeated "s” sound most likely relates to

the natural flow of the turtle’s actions.
the turtle’s difficulty building a nest.
how the turtle views the seasons.
how the sand feels to the turtle.