The interview process is new this year, however there are a few details out about what applicants can expect. It will be a video interview, most likely similar to a Skype call. There will likely be three questions to answer; two verbal and one typed. The applicant will have three minutes on each of the questions.
From my understanding, the reason for the interview process is due to the increased number of exceptionally high averages admission students have coming out of high school. At this point, the faculty know the students will perform well academically, however they now want students that will engage in the university's experiential learning activities and participate in other extracurricular activities. You are not likely going to find any sample questions, however the questions will focus on challenging students on what they have accomplished outside of school, what their goals and aspirations are, the types of academic and extracurricular activities they currently participate in, how they overcame potential obstacles in their high school career, if they have specific interests or projects they wish to work on at McMaster, or a particular team or group the intend to be a part of once accepted.
The faculty wants engaging, creative minds but they need reassurance that the students are not solely dedicated to marks alone. If your friend is able to prove this then she will have no problem completing the interview process.
I had no part coming up with the questions, however I'd imagine it wouldn't hurt to know a bit about the program she is applying to. If she is set on McMaster, she should do a bit of research on the engineering departments (Chem, Mechanical, Electrical, Computer, etc.) if she hasn't decided which to pursue, just to give her an idea what she may be interested in. If she has a good idea on what stream she wants, she could then look into any of the extracurricular activities and groups that associate themselves with each department (Solar car, engineers without borders, McMaster engineering society, IEEE student branch, ecocar, etc.). She may not be asked about them, but if she can express any kind of interest in these programs that the university funds, it could go a long way.
I hope this info helps, and If your friend sounds like the kind of person that is academically engaged as well as active in life outside of school, she should know that she is exactly the type of person McMaster is looking for.