It will come as no surprise that many things have changed for young women in the years since this book was published at the end of the 19th century. Happily, I wasn't reading this for advice but as a historical curiosity (although i did initially come across it after it was cheekily suggested that it would help temper my chippiness).
If I had been a 19th century girl, a small portion of this would have been rather sensible and illuminating (such as explaining menstruation and the uterus, at least putting right any fear that I was dying upon starting my period) although, thanks to the copious metaphors, I'd have also come away with vague notions of my body being both a piano and a furnace, and my lungs bellows, and convinced that simply being alive was morally degrading and/or physically dangerous.
I'd have learnt that it's terribly important to breathe, but that my thoughts must be pious and pure or they'd be poisonous and easily detected on my breath. I'd have learnt that eating too much causes not fat, but fits, and that exercise should be approached with caution. I should be forbidden from running up and down stairs, and may be injured by jumping. Dancing is morally objectionable and card-playing, while somehow considered exercise, can cause bloodshed.
I'd have learnt that reading romance novels can cause hysteria and even hasten puberty, and that during my period I shouldn't get my feet wet (although I wouldn't have learnt why). I'd have learnt that my periods should be pain-free and that if they aren't, it's down to my eating/doing/wearing/thinking something wrong. I'd have learnt that exercise was even more dangerous at this time, as it would make my "engorged" uterus sag.
I'd have learnt never to visit a travelling doctor or to take patent medicines (as they're all booze, and I'd become an unintended drunk), that getting drunk is a "most serious tragedy, with not an element of fun in it" and that by doing so I'd be risking idiocy, insanity and inebriety in my future children, whom I apparently do want even if I think I don't, as avoiding motherhood invites moral peril.
I'd have learnt that I shouldn't tease boys, that I'm responsible for his moral conduct as well as my own and that so much as letting him squeeze my hand may end in him having to visit a loose woman. I'd have learnt that so much as thinking about my own bits could inflame them, putting myself at risk of the "solitary vice" which "destroys mental power and memory, blotches the complexion, dulls the eye, takes away the strength, and may even cause insanity" and that I should avoid the friendship of girls, as "such friendship may degenerate even into a species of self-abuse that is most deplorable".
But more than anything else, I'd have learnt that the biggest danger to my life and happiness was tight clothing.