I'm not convinced about this being Silene. The allied genus Saponaria does tend to be mistaken and mislabelled as Silene in Indian gardens. This looks like Saponaria to me.
Generally speaking, one of the differences lies in the number of styles — 3 or 5 in
Silene vs. 2 in
Saponaria. Dimorphic (staminate/pistillate) flowers are known to occur in both genera. On close observation, a few 2-styled flowers can be discerned in Alka ji's photographs.
The calyx in Alka ji's plant is densely hispid. Hence, Silene armeria can be safely ruled out. Also, the pronounced corona present in the flowers of Silene species is absent/inconspicuous in Alka ji's plant.
Best wishes, Viplav