No one, and I mean absolutely no one, goes from middle class to gangbanger with the flip of a switch. Normally you don't change your mannerisms that fast.
Also from my understanding the corpo story does not begin with you being some low tier merc. You work directly for one of the higher ups in the "clean up" department, that just casually fried some people in the ESA council. You aren't a gun for higher like Smasher for example, you are clearly part of the company and delegate other people. You are defintely part of the office crew with heavy spy/agency tendendies. I agree though, that we knew someone like Jackie is quite weird, especially since it's not just some rando business contact.