The idea of having permanent residency somewhere is to live there. No country that I know of will let you keep PR forever if you do not live there. In Canada, it used to be 6 months you could be away in a year before you'd lose it. They changed that back in 2002 or 2003 and now their rules are among the most relaxed in the world, that is, you only have to stay in Canada for 730 days total in any 5 year period. That is less than 50% of the time and you can either do that all in one go and then be away for 3 years or you can do it with short stays.
This is simply a case of PR not being very important to your wife in the last few years and so she did not keep up with her residency requirements and now that she has decided that it is important, it might just be too late.
What is your status in all this? If you are a Canadian citizen, her PR would be protected for living with you in another country. If you are a PR whose PR is protected because you are working for a Canadian employer, same thing. If you are neither, there is a problem.
What she could do is wait it out in Canada and see if the immigration officer has reported her. If they decided not to, she could stay in Canada for the next 2 years without trying to renew her PR card and with that she would meet the residency requirements again. If they did report her or if she does apply to renew her PR card, her PR status would come into question. They would see that she did not spend 730 days in Canada in the past 5 years and so there is a question of humane and compassionate reasons why she couldn't meet the residency requirements but should still be allowed to keep her PR. That could be something like having to stay away to take care of a sick relative but staying away because of a job or because she was running a business would not be accepted as a good reason.
You can still try it if you want to. You can not apply to renew the card at the immigration office, you must fill out a form and mail it in, see http://www.cic.gc.ca/english/information/pr-card/apply-how.asp The processing time is now around 4 months but if you need it faster, you can go to the bottom of that page and follow the instructions there. If she doesn't have 730 days though, I do not think it will be fast. If she leaves during the processing time, that would negatively affect her application, that is if she makes a case that she is back to stay and wants her PR card but then they see she has left already, it would not look good.