Salam Aleikum sister SHABNUM,
hope to find you in good health, insha allah.
And, YES, it is allowed for a women to cut her hair, BUT for ex. if she wears hejab she will have to do it home, or somebody to do it for her, OR if she lives in a muslim country there are salons special for them, where the windows are covered.
If she doesnt wear hejab, she can go to the salon, BUT even there ONLY a women can do that for her.
I hope you understand, if not please feel free, and ask.