Hi Gauri
After reading what you wrote i can explain what happened with me. I was in a similar situation last year i.e. 2013. Was unable to meet 730 day rule but still had a valid PR. In one of the CIC documents OP-10 (Permanent Residency Status Determination) i had read that even if a person stays away from Canada for many years and than comes back and stays for 730 days , they will continue to be a PR. So a status is not lost. I took a print out of this document and kept it handy with me.
As i was waiting for my turn to Check In at China Eastern Airlines counter , the girl got furious when she determined that i was not meeting the 730 day rule. Please note she was just an airline rep , not even an immigration officer. I tried explaining her the things , but she took my tickets , put those on hold and told me to get out of the line. After i realized that things turned out of my way , i showed her the documents and asked for her supervisor. He seemed helpful and called CIC directly. They asked for my PR card number over the phone and told them to let me go and i was let off.
The people at Delhi Airport are least sympathetic. So , please ask your mother to take a hard copy of OP-10, just as a reference and also have them call CIC if they have any doubts. As per Law even CBS cannot deny entry , they can report someone , but not deny entry. So , how the hell can a airline representative , without consulting an immigration officer or CIC or their supervisor , not let a person go.
I hope this helped. Let me know if you have any more questions.
Thanks