We investigate proton emission from the highly deformed nucleus 131Eu within the angular-momentum-conserving core-quasiparticle coupling (CQPC) model. The calculations reproduce well the observed energy spectra and decay properties, and demonstrate that the dominant emitting configuration originates from the d3/2 spherical component of a deformed configuration, consistent with experimental assignments. Complementary calculations for the triaxially deformed nucleus 145Tm and the weakly deformed nucleus 151Lu further confirm that the CQPC framework provides a unified and reliable description of proton emission across a wide deformation range. The results highlight the importance of coherent single-particle-collective coupling in shaping proton decay from deformed nuclei beyond the drip line and provide a fresh perspective on the interpretation of decays traditionally assigned to deformed Nilsson orbitals.