Hi
I think the whole dynamic of an interview would change if done over the phone. I would think it's easier to hide a reaction to a question without having the person there in front of you.
I would think your girlfriend would have to travel to Sao Paolo for her interview - unfortunately a distance of 3 hours would not deter them from having a live in-person interview.
The phone interview is usually done with the sponsor who is residing in Canada, the in-person interview is with the applicant, unless both are in the country. Then the both the sponsor and applicant are interviewed in person.
PMM