So basically the semantics of an investigation rather than a crime. The type of thing the state resorts to if they still want to prosecute you even if they don't have a good case against you for the original crime?

Take the "making false statements to federal investigators" one for example, the "false statements" don't have to be at all related to the investigation (or eventual prosecution) at hand, they could have nothing to do with her personal financial matters, they just have to something you say that was not true during the course of the investigation.

Or "conspiracy" and "obstruction", both have a long history of providing law enforcement and prosecutors plenty of leeway to take punitive measures regardless of the feasability of the original case.

Very similar to the long history of 'resisting arrest' and 'assaulting a police officer' being used on a more localized level whenever a citizen did not show total obedience to police, regardless if they committed a crime or not.

all which was related to ~$45k? Hardly rational.

They usually get people for panicking when they're investigated. You never want to talk to federal investigators without a lawyer and you want to be very sure as to whether you actually remember things or not. People often play that safe by not remembering much of anything, but that can also bite you if you remember later.