If that is your ultimate goal then focus on getting her divorce first. Take it one step at a time. Complete step one then move on to step two.
There is NOTHING she can do about her previous permits and visas' stating she is single. NOTHING. Stop worrying about that part.
All she CAN do is when she finally gets around to applying for PR via the live in care giver option come clean and input all of the CORRECT information then. If she is divorced by that time, she would only need to include his information as an ex spouse. If she is remarried to you by then, she would include him as her ex spouse and you as her current spouse.
Can CIC come back and say hey, she never told us about being married in the first place. The simple answer is yes, yes they can. Will they? Who knows, its really up to CIC. As stated previously though, she can't do a damned thing about the past. You'll both just have to suck it up, learn from the mistakes and don't repeat them because ultimately, that is all you can do.
