Her heart was like a pine tree, dense, dark, protected by pointed barbs. But under all that, a thick sap, sticky and slow running. Or it was a field of grasses, leaning one way or the other in the wind; browned and bowing down or stretching up towards the sun, stalks thick and green.
Or neither of those.
Instead it could be like a stream, swollen with the spring rains, gnawing at the banks as it rushed for open waters. Most times, though, it was barren, cold, covered in yards of snow, wind-blown drifts, steep, sharp and high as hills.