In the game files, there’s actually a tech tree set up for the Boss General. It is indeed a massive mix of tech from all 3 sides. But her progression follow the Chinese line of Power, Supply Depot, War Factory, Propaganda Center (although I’m not sure about that one) then Superweapons.
Extra income is provided by Hackers.
Funnily enough, it’s the superweapons that actually contain faction-specific upgrades like hazmat suits or Extra Rockets for the buggies she sends at you.