Please help me talk some sense into my sister!

[Kaz]

I don't think you can "logic" someone into passion. Most people who know me consider me very logical and analytical, but almost all of my direction in life came from particular events that were very emotionally charged. If she is like me, and hasn't experienced something like that yet, any argument you could make probably won't have much impact. If I was in your shoes, I would just throw whatever influence I had on her into preventing disastrous decisions only, e.g. taking out those additional student loans. Double-down on things like that that are massive centers of gravity that can warp your life for years and years. The rest is probably out of your control.