Use of Vaniqa can reduce the frequency of having to shave, but it's expensive and has to be used every day.
Better by far to accept the fact that your wife has the sort of beard growth she has. And in fact a great many women have beard growth as heavy as men. Enjoy her for who she is and make sure she knows you love her as she is. Women with heavy beard growth are usually very much keener on the physical side of a relationship and usually much better at it, too.