With the increasing integration of renewable energy sources, advanced sensing technologies, and digital communication in power systems has heightened the need for resilient and the cyber-secure smart grid monitoring. This paper proposes a sustainable and cyber-resilient phasor measurement unit (PMU) deployment framework which is formulated as a multi-objective optimisation that simultaneously considers the cyber-physical attacks, economical metrics, and operational sustainability. A novel composite vulnerability index (CVIndex) is developed that integrates the topological criticality (via. Hybrid Betweenness Centrality) with operational stress factors such as the line loading conditions and the voltage stability indices. Building upon this, a bus-level risk aggregation model is proposed to quantify the attack exposure by integrating probabilities of cyber threats, network fragmentation impacts, and operational stability factors enabling targeted PMU deployment for maximum security. To solve this complex optimisation problem, a novel graph neural network (GNN) is proposed that simultaneously minimises the economic expenditure while maximising the system resilience under cyber threats. The proposed method is applied on IEEE 14-, IEEE 30-, and IEEE 118-bus test systems to evaluate the efficacy. The results demonstrate the ability of the proposed approach to identify PMU configurations that enhance the resilience around 45% at a lower economic cost of 15% by providing multiple solutions compared to evolutionary techniques.