Welcome to the forums - I'm so sorry that you lost your daughter to this brutal disease, but I'm glad you've found us.
Women do worsen after delivery, sometimes. Some of our regular volunteers are even raising their grandbabies because their daughters worsened after delivery. Delivery starts the healing process in motion, but there's substantial repair to be made and the chemicals that cause the symptoms are still in your bloodstream for some time postpartum, where they can cause further damage. I don't know if any of our current active posters have gotten worse postpartum, but we do see it here regularly.
These conditions are strongly tied to underlying autoimmune conditions including diabetes and lupus, but like your doctors, I'm suspicious of the idea that you have autoimmune hepatitis. Since we know that some women worsen after delivery and take time to heal, it's hard to say much for certain - especially with an inconclusive biopsy and a positive trend! Do you have another followup scheduled?
Most women who develop this cluster of diseases (gestational hypertension, preeclampsia, eclampsia, HELLP syndrome) in a first pregnancy are at high risk to develop it again in later pregnancies. That said, in those later pregnancies it generally appears later, in a more mild form. This is thought to be because the area of the uterus where the first placenta implanted is developed in a way that makes it easier for other placentas to implant. Although most of our posters have had later and more mild onset, some worsen with some later pregnancies - or have a successful second pregnancy and then a loss in their third pregnancy. Thank goodness, this doesn't happen often, but it's something to take into account.
A pregnancy achieved through any sort of fertility treatment is at higher risk for these conditions. This is because they're thought to result from a "dysregulated" implantation and what the researchers call "breakdown of maternal tolerance," which essentially means that the placenta, which is a foreign organ, wasn't able to coax your immune system into ignoring it, for any of a host of reasons (so far as researchers can tell at the moment, mostly genetic ones - and this is one reason it varies so much with each pregnancy, as each sperm has wildly variant genes from the swimmers next to it.)
Lots of us were really healthy. There was nothing you were doing wrong! The correlations between these conditions and lifestyle are exceedingly poor to non-existent. There is a known dose-response curve with obesity - the more you weigh, the higher your odds - but it is a shallow curve. Your odds curve upwards, but gently, especially at first - and even women who are underweight experience this disease with a pretty steady frequency at around 2-5%. That number is fairly constant worldwide, with spikes for infertility treatment in the countries that have it as readily available medical care. Currently, they're thinking that both a genetic predisposition to preeclampsia *and* some environmental influence from obesity are in play when a woman with a BMI over 30 gets pregnant.
There is no known treatment or therapy for this condition, apart from some very slight benefit from a daily baby aspirin that only appears in meta-analyses, calcium supplementation in extremely calcium-deficient women in Third World countries (supplementing US Americans had no effect), and some preliminary work on metformin for diabetics. But monitoring women closely allows for the timing of steroid shots for lung development and for delivery before women get critically ill and for transport to a good NICU if one is not close by. (Some of our posters live in parts of the country or the world where they need to travel to a good NICU.) Many of our posters have some sort of underlying condition like PCOS or chronic hypertension that needs to be managed to reduce the risk of "superimposed" preeclampsia, or preeclampsia on top of another runaway condition.
MFMs, maternal-fetal medicine specialists, or perinatologists, or high-risk pregnancy doctors, are precisely the people you want to be seeing. I'm glad you already have a relationship with one. Hopefully we can help you sort out which questions to ask at your next appointment so that you can make a concrete plan about a next pregnancy.
I hope this helped - and this place is completely huge, so holler with any more questions!