  Recent neutron scattering observations by Plumb et al. [1] reveal that the
ground state of $FeSc_2S_4$ is magnetic with two distinct Fe environments,
instead of a quantum spin liquid as had been previously thought. Starting with
the relevant O(N)-symmetric vector model of $FeSc_2S_4$, we study how the
discrete ($Z_2$) and continuous rotational symmetries are successively broken,
yielding nematic and ordered phases. At high temperatures, we find that the
nematic order parameter falls as $T^{-\gamma}$ ($\gamma>0$), and therefore,
$FeSc_2S_4$ lacks any distinct nematic ordering temperature. This feature
indicates that the three-dimensional diamond lattice of $FeSc_2S_4$ is highly
susceptible to the breaking of Ising symmetries, and explains the two distinct
Fe environments that is present even at high temperatures, as seen by
M\"ossbauer and far infrared optical spectroscopy.
