teaching experience alone may not be appealing enough
since after all, it's a business school looking for people with not only ambitions but also exposures in business, or even better, management.
that said, your fren still got two years to add other interesting experiences into his/her portfolio. Start-up experience is highly valued. Community leadership is also helpful. Exceling in his/her full-time job is a must of course.
One thing about INSEAD is its diversity. There are people from all sorts of backgrounds, from actors to journalists. These applicants are minority of coz, but positioning him/herself properly, he do have a shot.