If it is V-1 then it is not a super visa. It is a TRV (Temporary Resident Visa).
Your mom has applied to extend her visitor status which will expire in December 2017, whereas the actual validity of her TRV is until June 2018.
The visitor visa enables someone to travel to Canada, whereas the visitor status is what is granted at the POE when her stay is assessed by CBSA, or like her present situation where CIC has allowed an extension to her visitor status. Hope this helps to understand the difference.
Your mom can apply again to extend her visitor status (approx. 30 days before her current visitor status expires). But, do note that if it appears like she is living and not visiting then it could be refused/shorter stay could be allowed.
Ideally, she must return to her home country and remain there for some months before she can attempt to reenter Canada before her TRV expires in June 2018. If her passport is expiring in June 2018 too then she must first renew her passport and travel with both passports.
Alternatively, she must return to her home country..... wait for some months..... before applying for a super visa from scratch. Super visas cannot be applied for from inside Canada