Fiduciary duty is a tricky thing with multiple perspectives. From the business community’s perspective at the time the developers did not do their duty with regards to limiting transactions with a blocksize limit that rendered many Bitcoin businesses unable to continue their business models.
I think in this case she’s referring to fiduciary duty to those that use their code from her perspective of making sure proper laws and regulations are forcibly adhered to.
If you were government, you would want the ability to reverse transactions due to fraud.
It could mean that.
Of course, this breaks the point of crypto, which is to have a democratic peer to peer ledger.
And you'd have to have some authority to prove that to (which would be a government).
That sort of thing would cause a fork in the country that tried to enforce that, with that country's fork lowering in value.
Eventually, those people who owned on both forks would move to the stronger peer to peer fork.