A Witch

[Brownlie]

This is pretty cool. There are some metrical hiccups, but I think they may actually add to the style here.

There's a hill bowed alone under clouds, -- Alone to under reads as spondee to me.
Woven with roots and the long hair-- W shouldn't be capitalized. Fixing the capitals would be a quick fix for the poem.
of wild grasses, wildflowers and forget-me-nots. -- I'm not a flower expert. The sound is cool in this line, but is a forget-me-not a wildflower? There are also seems to be some redundancy with the repetition of "wild," but it may be justifiable.  
Come night, she arrived with bare feet
To tip-toe a slow, wandering path,
Until she reached the peak. -- There is a sort of clarity, but there are also generalized words like peak or bare feet or wild grasses that may be enhanced by more detail.
Then she drew back her shoulders, and sighed, -- If you put back after shoulders it would read more rhythmically clear to me, but I like your positioning.
Hard. So the breath left her lungs like an animal -- Maybe a more specific animal.
From a dirty cage. The hill wore the sky
As a big cape,
And it began to cry for her.

So the clouds took her poetry
and hurried to replace it with grey fog.
Next, their rumbling stole her hunger,
Reaping first her belly then her heart. -- I'm generally skeptical of heart, but perhaps you could work it into your overall style. As long is its not in a collocation like bleeding heart or something.
Starry black fists digested it as it climbed,
They packed it into the air, so it became the thunder.

Like this her life’s crack-bam and zitz-zic-schrak,
Cut open the night as great blades of lightening,
And spilt into a Storm like boiling car-oil.
At each shot of the starter-pistol -- Interesting segueway
Races began between frights of tearing wind -- I think between frights may be a spondee, but a few spondees may be good.
Which rode as horses across the flashing night.
A mania like rapture stirred the sky
Into a battlefield, a playground, a murderer.

So the Eye dropped to her knees soundlessly, -- eye of a tornado?
Her blue lips flat-lining, her lids half-closed.
She pressed the length of her body,
Still and white to the waves of sodden ground.
And though a storm will only last so long,
Time passed, and she grew colder.

And as the storm rose up
she started to die.

Seems cool. I left some comments that may or may not be helpful.