One of my friends interviews people for MIT - it's been a year since he graduated so I think he is 23 (same age-group). From his point of view as long as you are dressed neatly, it's all good. When I had my interviews, way back, I always put a suit on but nowm looking back, I think it was an overkill. I'll interview people next year and I think if anyone would show up in a suit, it's think they made an effort, but not in the direction that matters :). I don't think GQ style is good either - you are not trying to make a fashion statement. If you are really worried, feel free to ask her, othervise dress neatly.