After the mission of eliminating the three remaining stalkers in Eliza's employment. Zane and the girls immediately retreated back to the safety of Gravestone. Or as relative as safety could be in this apocalyptic world.
Eliza, for whatever reason, had chosen not to send wave after wave of attack towards Gravestone, something that New Reno commonly had to deal with from Bart's attempts to break their resolve and weaken their forces.
The reality was that for every wave Bart sent towards New Reno, sure; the survivors lost people, but the resources gained from the successful defense only further bolstered the strength of those who remained.