Julia, you point out something valuable to be aware of. Birth control pills are often progestin plus ethinyl estradiol (both chemically stabilized compounds related to the biological hormones), which I also wouldn't use for this purpose. Some people may prescribe them as HRT, and some people still prescribe Provera (containing a complex of estrogen compounds purified from mare's urine) as HRT, but I am referring to bio-idential hormones used for HRT. I prefer skin formulations because there is some data which shows that oral formulations even of bio-identical hormones could have some counterproductive effects due to "first pass" through the liver considerations.
(I'm pretty familiar with all the chemistry of the compounds, natural and synthetic, and the medical literature. I did research in this exact area for a few years when I was working at a pharmaceutical company and I still follow the original papers that come out as it's a matter of personal interest to me. So I'm kind of a geek about this topic!!)
I'm glad you found something that works for you, I'm not discounting it. It's another valid option. That is why I am suggesting she see a specialist. Risk and benefit needs to be considered on a per patient basis...
A co worker once announced "you know, I didn't think going through menopause was all that bad", to which several of us replied, "maybe you should have asked us what going through your menopause was like"