It was mentioned this way online$5000 is low. I would recommend she hold off applying again until your parents are able to increase their savings. While she may be staying with family while in Canada, IRCC wants to see that the applicant has sufficient funds to cover all costs related to the trip on their own.
Since both you and your brother (?) both have PR, IRCC may be concerned your mother has plans to remain in Canada long term. Because you only recently landed, it would probably be a good idea for your mother to wait a few months before applying again and then request a two week trip only.
*In general, an individual foreign national mayneed to provide “proof of funds” in the amount of approximately $1,230 CAD per month, so if you plan to bring at least $2,000 CAD for this 30-day tourist visit, that should be adequate in terms of the Canadian visa application*