Yes, same Countess Bentinck. It should be said that other than Lehndorff here, everyone describes her as attractive (including Catherine the Great in her memoirs who had a girl crush on her as Bentinck was the first woman she saw riding and generally being cool), so either it's one of these cases where someone is attractive due to their charm, independent of their looks... or Lehndorff was just a bit worried she might convert Heinrich after all. (Her portrait doesn't tell, as it's a standard 18th century female portrait, and unless we're talking older women, these all look alike.

She left her husband, btw, i.e. "Gatten" (Gatte in the accusativ), not "Galten".

Peasants: sigh. Yeah. It has precedent: The Great Prince Elector (aka Fritz' great granddad) once had the citizens of Berlin and the citizens of Spandau (then not yet a part of Berlin) beat each other up for his entertainment. They got paid, too.

So I think this is making a joke about marrying her for her money??

Yes. "Despite having been a grandmother since four years, she's about to marry a young man who weds her for the beautiful eyes of her treasure box."