I came to Canada on a work permit.
Mine was tied to my job and my company.
It was valid for 2 years. It was extended twice until I eventually was granted the status of a Permanent Resident.
The work permit of your girlfriend should state for how long it is valid.
It should also state what type of work she is permitted to do under the permit.
You might not be able to attend a university, college or other educational institutions under that work permit.
Please check carefully.
I knew this as "Work & Travel Visa" from other occasions. It's definitively different from what I did. But my daughter did it when she came to do a stint for a month.
The Working Holiday category is designed for Swedish citizens who intend to travel in Canada and who wish to find temporary paid employment to help pay for their stay (maximum 12 months).
So if I read the web page correctly then your girlfriends visa will be valid for 12 months.