Well, My Fiance had long hair as well, now she wears it in a cut which is not longer then to her chin. Its her Hair and her choice. Its much easier for her for work and everything, and much easier to take care of.
What do you love ? The women or just the Hair ? No need to cry since the woman you love wont change, only her hairstyle. After i saw my fiance with her new cut i must say she looks much better then before because she looked way to thin with the long hair.
You hopefully picked her to be your love because of the whole person she is, not only because of her hair. Enjoy her changes, because i am sure you wouldnt her to complain either if you might start to go bald one day...