"She leaked the documents to Wikileaks, who decided to publish them uncensored. She had no control over what Wikileaks would do."

The first part of your sentence shows why the second part is nonsense. Manning dumped a bunch of classified information on a third party. Manning left the ethical decisions to that third party. That is certainly preventable as many others have prevented it. I've done so many times with confidential information that I make public in a selective way in my writing that protects sources or just details that must be private.

Truth is Manning's mind was messed up due to internal struggles, she also saw messed up stuff in military, and simultaneously was blindly trusting third parties to make the right decisions. The combination led to a damaging, criminal decision to turn all of that over to Wikileaks rather than pure whistleblowing of combing for corruption to selectively leak and/or redact. This is what she was rightly punished for although how the punishment was delivered was cruel and should've been illegal.

Glad Manning is to be released soon but she set it in motion with foolish decisions that had alternatives. It certainly wasn't an inevitable set of cause and effect.