What natural supplements are the best for estrogen replacement.?

My wife had a hysterectomy after our last child (ovarian cancer) she was fine at first but now at 34 she is having symptoms a middle aged woman might have (hot flashes night sweats menopausal type things) recently we had to take her to the emergency room and they ran a blood test and said her estrogen levels were too low for her age and she needed to get to her doctor for a estrogen rx. insurance isn't the problem. My wife doesn't want to take estrogen or progesterone but is willing to take an herbal supplement that might alleviate some symptoms. basically without getting an rx is there any supplement out there (i heard soy is one) she can take that would relieve these symptoms?