I wouldn't really count on this, tbh. Not only August is a businessman first so if he sees potential for profit, he's likely to take advantage of it (whether it's by extracting favor from Edwin or Rosie herself) but also Edwin being on great terms with August isn't guaranteed to be the case forever and no matter what.Rosi owes nothing anymore if you are on great terms with August!
In a way, Rosie in this scenario becomes a hostage of sorts, where her further well-being depends on Edwin playing nice with August so that you don't piss him off.