Normally Va is calculated with MTOW and kept contant if weight is reduced.
It´s not the g´s that load your airframe, but the total lift force which bends the wings. At lower weight the wings stand higher g´s and vice versa. The aircraft primary structure is normally designed for MTOW or for maximum zero fuel weight (especially for any airplane having wing tanks). At lower weight it stands higher g´s so it is accepted that your Va now allows for more than the design acceleration and therefor no VA reduction is required.