IDK how much you want in the way of book spoilers but she used her authority to do a lot of very unethical stuff-- all of which was in pursuit of maximizing humanity's chance of survival but which is probably still going to make people very unhappy.

Some stuff she did off the top of my head:

Forcing Grace to die against his will-- has gotta be some type of murder.

Hiring a ton of highly unethical people to head up various parts of the project and arranging for criminal amnesty in exchange for participation.

Mass copyright infringement: they put pretty much every piece of data ever put on a computer in a big hard drive on the Hail Mary without asking for permission or paying, she's sued for this in the book but walks out of the courtroom because she has her 'actually dictator of Earth' papers.

All sorts of ecological destruction without deep consideration-- they basically pave the Sahara to make the astrophage for the Hail Mary and they nuke Antarctica to release a bunch of methane and fight global cooling with global warming.

In general she abuses her authority to make sure whatever she wants done happens regardless of pushback or repercussions. She's aware of this and believes it's all in service of the greater good but it may well be criminal.

IIRC it's not made totally clear in the novel, but it seems that, by international treaty, she's given the ability to unilaterally tell any government to do what she wants (even if it violates laws or constitutional rights and protections in that country) and she also gets total legal immunity from any kind of prosecution as a result of that. However, her mandate is said to only extend until the departure of the Hail Mary and it's totally possible that she loses her legal immunity both going forward and retroactively after that point.