If you apply inland, you should send along with the application a request for extension of visit status and a request to change status to open work permit upon first stage approval. That way, it's all tied together. If the first stage approval takes longer than 6 months, her visit status would be automatically extended and she would get her work permit right away at first stage approval rather than have to apply for it at that point and wait for it. If all goes well with the first stage approval, she can expect to have the PR in another 6-12 months after that.
For inland, it's is very important to have all your i's dotted and t's crossed. If they find any problem with your application and decide that they want an interview, she will not get a first stage approval in 6 months but instead will have to interview at your local CIC office where you live. Depending on their caseload, these interviews can take up to 3 years to get and in the meantime, she would have no work permit and no health care. Another downside to inland is that you are not advised to travel while it's in process. Any problem with her family and she has to go back, she risks not being let back in and losing her inland application.
If you decide to go outland instead, you can still request a visit visa extension. It would take 1-2 months to approve you as a sponsor and an average of 8 months in Argentina to get her PR. The downside is if they called her for an interview, she would have to go there.