Your mother needs to submit police clearance records for every country where she's lived for 6 months or longer after turning 18 years old.
More info here: http://www.cic.gc.ca/english/information/security/police-cert/mid-east/saudi-arabia.asp
"If you are applying at the Canadian Embassy in Abu Dhabi, UAE, you should submit the police certificate with your application. You can contact the visa office for a request letter at fax: (971 2) 694-0396 or e-mail: abu-dhabi-im-enquiry@international.gc.ca Please include your immigration file number if you have one."