What do I know?
1. She was born on September 7, 1777, and lived to November 23, 1858. That's a good long life -- 81 years.
2. We can assume she was a strong and healthy woman, to live that long!
3. Her parents were Peter Otten (1737-1792) and Anna Jachens (1737-1786). Not so long-lived, either one of them.
4. She must have been close to her brother, Johann Harm Otten, because he and his wife named their daughter -- Anna Margrete Otten -- after her.
Where did this information come from? From a treasure trove of info I found in an Ortsfamilienbuch (OFB) for the Lesum area of Bremen, Germany. I found many, many ancestors of my great-grandmother, Christiane Bellmer.
What else can I figure out? Peter Otten is listed as 1) a farmer, 2) a laborer (1780) and 3) a day laborer (1781). Since I assume these are listed in order, he went from a farmer to a laborer (three years after Anne's birth) to a day laborer, suggesting a downward slope of his position in the world. Did he have a farm and lose it? Why? Did he drink, gamble, become disabled and therefore not able to run his farm? Since the OFB offers no information on Peter's father, Dierk Otten, I don't know whether the farm had been in his family.
Anne seems to have married fairly well -- her husband, Johann Friedrich Fastenau, was the owner of a house and a small piece of land, and was a "wood sawyer." She was mother to 10 children, only five of whom survived into adulthood.
So, that's the best I can do for my near birthdate-mate. I'd like to find out more!