Well, if Dr. Zimmermann - he of the broken penis theory - is to be trusted, the problem was that Fritz didn't want to be seen in the nude by anoyne, which if your dead body gets embalmed is inevitable, whether or not there's an autopsy first. This might have been SD's reason as well. Caveat here: as among other things the detailed "last days and funeral" report felis unearthed shows, dead nude Fritz was, in fact, seen by several someones, not least because his body was cleaned up from head to to and dressed in a uniform, which he had to know would happen even if he had gotten the funeral of his choice, so forbidding embalming for that reason alone would have been illogical.

Now today, I know a good share of people who don't want to be embalmed, but they usually buy burial places under trees in a "Friedwald" so their dead bodies can become one with nature, if they don't opt to be cremated to begin with. Wanting to become one with nature definitely wasn't an option for SD, though! So I'm left there with "she probably thought doctors cutting her open would be terribly undignified"?