Visa Situation

Hello r/Belgium, hope one of you might be able to help me with my current visa situation. So I came from Canada to do my PhD in Belgium and my contract and visa are both running up at the end of this November. Problem is that I will probably need an extra month or two (or three) past this time to finalize everything for my thesis defense. I thought it would not be a problem since I have been legally cohabitating with my Belgian girlfriend for the last 2 years. However I went to my town hall office today to see what kind of docuements I would need to bring in and explained the situation to her and she said that there may be a minimum that my girlfriend would need to earn for me to be able to get a visa. The earnings she said were if I was still considered a student and were 1800eur/month, but since I wouldnt technically be a student anymore she was going to call Brussels to see what the situation would be. Wash oping I might get some more information here!