Unless you are a Canadian citizen yourself, her PR status would be out the window by now for lack of residing in Canada. Her PR would be protected if she were living with a Canadian spouse overseas.
However, even if that is not the case, immigration does not track the whereabouts of every PR so it is unlikely that they have officially revoked her PR. Therefore, it may be possible for her if she is visa exempt to enter Canada without attracting attention and stay for 2 years in order to put her PR status back in good standing.
The rules before PR card were that you had to stay in Canada 6/12 months to keep your PR status alive and after PR card until present, it's 2/5 years. There is a loophole in the regulations for a person who was a PR but hasn't met the residency requirements but has somehow managed to get back to Canada without being reported and therefore never lost their PR officially.
If such a person manages to stay in Canada for 2 years, their PR status will be back in good standing and they can apply for a PR card. This is because immigration is not allowed to go back in time further than 5 years. If she didn't get caught by them at a time she didn't meet the residency requirements, they can only look at the past 5 years by the time she applies for a PR card, by then having stayed in Canada for 2/5 years.
If she manages to enter Canada, she is still a PR. If she has her old landing papers, she can prove it too. Her SIN will have been deactivated after such a long time. She must go to Service Canada and get it re-activated. Not having a PR card could give her problems when applying for health care, a new drivers license etc. During the 2 years after arriving in Canada, she should not risk leaving and she should not apply for anything from immigration. Just lay low and wait for the 2 years to pass. After that, her status would be in good standing.
If you are not a Canadian yourself, that would however be a problem for you because she would not be able to sponsor you during that two year period. You could visit if you are visa exempt or try to qualify for your own work permit which is not easy.
If she gets reported on entry, that is when the immigration officer realizes that she is a PR who doesn't meet the residency requirements and writes up a report in order to revoke her PR, she can appeal and she can stay in Canada during the appeal processing but she has a very low chance of winning the appeal if her living outside Canada was by her own choice.