Intermittent break failure brand new Mitsubishi Mirage

My daughter's Mitsubishi Mirage is brand new, we bought it last summer. It has maybe 8000KM on it. It's had one regular service at the dealership, no other maintenance.

Yesterday my daugther got in the car, turned it on, saw a bunch of lights that she didn't recognize that then went away, and noticed that her car was vibrating more than normal. She then pulled out of our driveway and as she hit the bottom of the hill of our driveway the brakes did not work. She had to throw on her emergency brake or risk rolling out into the road.

She put it in park, turned it off, came back up the hill and got me and I came down and checked it out. She turned it back on, I noticed the vibration too but no lights, I had her test just inching forward a bit and hitting the brakes and they seemed to work ok. So, she decided to continue on to work. As she drove down the road she came to a stop sign and hit the brakes and again they didn't work.

Now it's at the dealership and they're saying they can't find anything wrong. They say they've taken it for a test drive and found nothing wrong. What should we do?