Hmm. If you look at this fertile woman's pregnancy record, the only time she takes more than a year to get pregnant is in 1727. Assuming for the sake of the model that she gets pregnant 9 months to the day before giving birth, there's a possible outlier here:

December 19, 1721: Gets pregnant 6 weeks after marriage.
March 6, 1723: Gets pregnant 5.5 months after giving birth.
June 13, 1724: Gets pregnant 6 months after giving birth.
January 23, 1726: Gets pregnant 10 months after giving birth.
December 5, 1727: Gets pregnant 14 months after giving birth.
April 3, 1729: Gets pregnant 7 months after giving birth.

Right around the time she would normally have been getting pregnant (April 1727), they're all busy fleeing the country. The angry letter from Augustus to FW over the hanging incident is March 28, 1727. Now, she could have had a miscarriage sometime in 1727, but I wonder if she did stay in Dresden for a few months, separated from her husband, before they decided it was safe for her to come back to Berlin. (Realistically, she was probably in Berlin in 1730, but for maximum angst reasons, I want her to have fictionally died in Dresden.)

Side note: Would not be an 18th century woman for anything!