Let's see, FRS attacks at a cellular level, like what Tsunade said it is akin to poison.. Tsunade's Strength of a Hundred Healings is an extension of Creation Rebirth.. Creation Rebirth does not heal damaged cells, rather it hastens cell division which allows the body to re-generate tissues/organs, etc.. so in theory, even if FRS destroys Tsunade's cells, Strength of a Hundred Healings would allow her to create new ones in replace of the old.. even if FRS destroys that cells, chakra network, those cells can be left alone to die as Strength of a Hundred Healings would create new ones.. it would be a continuous process of cell destruction and regeneration.. it would all fall down to how much chakra Tsunade has, and since seeing her Strength of a Hundred Healings can last to at least several hours, there is no doubt she can tank it..