M.,
I would think a divorce is 50%/50%. Your friend should ensure that he has copies of all bank statements, financial funds, assets, etc. from 3-4 months before they decided to get divorced. I think sometimes people who WANT the divorce start squirreling away money without the spouse knowing it. They are trying to "get a jump" on what's to come.
I had a similar situation with the death of my father. My brother tried to take money from his bank accounts and claim to know nothing about it. I worked with the bank to get statements from before my father died. Then I worked with the estate attorney, with EVERYTHING documented (both with the bank statements and with my own spreadsheet showing the "eligible/legitimate" expenses I knew about.) The attorney then took the spreadsheet to my brother and notified him, whatever expenses you can't substantiate, YOU are responsible for.
I think the same should be true for your friend. He should do everything he can to prove what they owned before all of this started. Then keep a spreadsheet of questionable or downright obvious abuses, then let her explain herself. I think it's very reasonable to assume that these are still "marital assets" that need to be divided equally in the eyes of the court. (Note: He should have a spreadsheet that "totals" all that he thinks he is owed. If he is honest, I think it is more likely that things will work in his favor.)
Best of luck to him.