Hi scrunchy- what a lot your family has had to deal with in the past couple of months!
It is my understanding that the preeclampsia headache is caused by the swelling, not high blood pressure. The swelling causes intercranial pressure which triggers the headaches. So, if she's been on diuretics and her swelling has resolved for the most part, my uneducated, non-medical guess is that it's probably something else causing the headache.
For most women, the preeclampsia will start to ease with delivery, and the greatest risk is within the first 48 hours. It's true that it can persist up to six weeks, but developing eclampsia at that point would be incredibly rare- and usually (and I say usually, because women here have experienced a great deal of variety in their experience) most eclampsia is a result of severe Preeclampsia- BP's exceeding 160/110 and 5,000 mg protein in a 24 hr urine. When I had postpartum preeclampsia (and THE headache) it was within 10 days of my baby's birth and my swelling had gotten worse rather than better.
How did her anesthesisa go? When I had my first, my swelling, like your daughter's, was very bad. The anesthesiologist had a really hard time placing my epidural and she missed the spot, nicked my spinal cord, and triggered a 'spinal headache'- a miserable, painful headache (the God's honest truth, one of the worst pains in my life- worse than labor, even) that didn't go away until they did a blood patch. Sometimes, the providers don't like to suggest spinal headaches, because they're the result of a mistake by a provider, and will eventually heal themselves. But, if your daughter was really swollen, it could be a possibility! Best wishes, and I hope she's feeling better soon!
Allie 5-13-98 (35 weeks-pre-e)
Baby Camille 4-17-03 (36 weeks- htn and oligo)