بسم الله الرحمن الرحيم
It is lawful in itself for the women to shave the pubic hair by razor but it is not desired, they should shave it by hair remover cream.
Note: If this razor performs like waxing or even better i.e. it maintains the softness of the place then its use shall not be undesirable too.
Allah knows Best!
Darul Uloom Deoband