You can buy estrogen without a prescription from the same sort of grey market places male-to-female transsexuals use. Phyto-estrogens can otherwise help, but I do not know by how much. That being said, you should probably find a knowledgable endocrinologist rather than trying to do things yourself as female hormones are extremely complicated. Depending on the phase of the menstrual cycle, for instance, ~100 can be in a normal range, though you don't mention anything about that for a reference. If she hasn't had a hysterectomy, women also ought to take a progesterone supplement as well as taking estrogen on its own can increase the risk of cancer, particularly as far as the reproductive tract goes. Finally - and most endocrinologists don't even know this - women produce more testosterone than estrogen, given testosterone is the parent hormone from which some estrogen will be derived from. So again that adds another element of complexity of possibly deciding to run TRT instead or otherwise making sure whatever estrogen she does supplement does not throw things off there.