Accurate determination of the full momentum-dependent spin susceptibility is very important for the description of magnetism and superconductivity. While in principle the formalism for calculating in the linear response density functional theory (DFT) is well established, hardly any publicly available code includes this capability. Here, we describe an alternative way to calculate the static , which can be applied to most common DFT codes without additional programming. The method combined standard fixed-spin-moment calculations of with direct calculations of the energy of spin spirals stabilized by an artificial Hubbard interaction. From these calculations, can be extracted by inverting the RPA formula. We apply this recipe to the recently discovered Ising superconductivity in NbSe monolayer, one of the most exciting findings in superconductivity in recent years. It was proposed that spin fluctuations may strongly affect the parity of the order parameter. Previous estimates suggested proximity to ferromagnetism, , peaked at . We find that the structure of spin fluctuations is more complicated, with the fluctuation spectrum sharply peaked at . Such a spectrum would change the interband pairing interaction and considerably affect the superconducting state.