In my opinion she was just a figurehead, dummy but not stupid. Nobody knows the real masters of this scam and who stood behind the scene but to run such a scheme you must have big money too.
Exactly this! I'm from the same country where "Ruja" is from (Bulgaria) so there're plenty of news in our own language which no one bothers translating. My country is famous for 1 thing, that no matter how big of a scam you pull, you can always get away with it and that's exactly what Ruja did. However same as you after reading numerous of articles, I'm 98% sure that she's not the mastermind behind it but most likely someone even more influential who's standing above her and her brother and pulling the strings. Some are even saying that she's already dead so any traces leading to the original founder can be eliminated. When it comes to her brother, he's under the USA witness protection program, so he's OK.
Based on what I've read and her history (she attempted another scam called BigCoin), it sounds like she was only looking to make a "modest" amount of money. She intended to make tens of millions, but Onecoin brought in billions. After a certain point Eastern European organized crime took notice and kept it going.