So you, being the arbiter of morality, think what Sam did was more acceptable than what Donna did.
I don't think what either did was acceptable.
However, I can understand how Sam may have thought that what he was doing to Jonas was ultimately in Jones's best interests as well as Sam and Jock's best interests. The plan was supposed to turn out mutually beneficial for Sam, Jonas, and Jock.
Both Sam and Jock may have thought there was such a great potential benefit in what they were doing, that committing Jonas was justified. The thinking being: Jonas will have to spend some time in a sanitarium but drilling on his land could make all of us millionaires, including Jonas. We're doing a good thing for all of us and Jonas will thank us later.
In Donna's situation she's telling the public stuff that is none of their business whatsoever. She's invading Sam's privacy and distributing the contents of his diary without his consent. Donna is sacrificing Sam's memory and legacy and betraying the trust Sam had in her so she can make money and get her name more well known. Where is the benefit to Sam's legacy? There is no intended mutual benefit, unlike the plan involving Jonas. It only hurts Sam's legacy and helps Donna. There is no reciprocation, no benefit to Sam and his legacy as well.
Sam may have thought: I'm justified because the potential benefit to Jonas far outweighs the short term downside to Jonas. How could Donna have thought she was justified in sacrificing Sam's legacy and betraying his trust in her just because it was of benefit to her?