Hi guys, anyone have any experience getting a student visa/ visitor visa to study a short term course at yoobee or Weltec before?

There are courses like the certificate in digital media and certificate in creative technology which runs full time study for approximately 13-17 weeks. As i know with a visitor visa we can study up to three months. What options do I have if I want to take these courses in NZ? Can I apply for a visitor visa of 4-5 months If I get prove from Weltec detailing the length of the course?

Im asking this for my cousin and she is keen to come into NZ as a visitor while doing a short course and visiting the country!