As long as she has a PR card or a PRTD which she will need to board a plane she will have no problem at all returning given as a PR she is entitled to enter Canada. In any case the residency obligation is 2 years out of 5 years from initial landing and she has only been away 8 months and only becomes an issue if she stayed away without returning at all until November 2021, but August 2020 is no problem at all. .