I think I was not clear. Her multiple visa expires on 30th July 2020. She landed here on 26th January 2017. Based on that she should not living here for more than May 26th 2018 at a time (max 6 months stay at a time). I heard people are driving to US and coming back and that is working. Just wanted to confirm with very experienced and helpful canadavisa folks here
Let me know. Thanks.
A multiple entry visa assumes that the holder will leave Canada at the end of their authorised stay, return home for a while often for same period they stayed in Canada before returning.
So whilst you could exit the country to the US and come back in straight away there is no guarantee at all of getting a fresh 6 month stay especially if you are faced with a CBSA officer who believes your mother is no longer just visiting temporarily.
This is why the advice on here is to use the extend stay as a visitor process without leaving the country at all given whilst there is stil no guarantee it would be far less risky than leaving the country given processed by IRCC not CBSA at the border.
Ultimately the decision is yours to take and whilst some will say it is not an issue to do a border run everybody who enters Canada is assessed at the border as an individual, there is no one assessment or outcome that fits everyone. Avoid the stress and use the extend stay as a visitor option, your mother even gets implied status whilst waiting for a decision and if doesn’t work then go for the exit/entry option.