We extend our previous quantum many-body Green's function formalism to characterize the deformations induced in the electronic structure of a quantum emitter when it strongly couples with a plasmon-supporting environment at finite frequency. Through infinite-order perturbation theory, we predict the emergence of subtle yet observable changes in the plasmon-dressed molecule's frontier orbitals, orbital energies, and low-lying electronic excitations when the molecular and plasmonic systems are resonantly coexcited. These distortions, which predominately arise from the finitefrequency image interaction, point to new chemical and optical properties beyond those of the vacuum molecule and bear impact upon resonant plasmon-enhanced molecular spectroscopies and hot-electron-driven chemical catalysis. We propose an experiment capable of testing our predictions.