That kind of commute will definitely put a strain on a relationship. I drive 45 min each way at the moment, and a bad commute does effect my mood, especially after 8-9 hours of working. I can't imagine 4.5 hours a day.
Honestly, you should just get a new job near her school. The reduced cost of rent, and commute should cover your student loans. Also, with the extra time, you can cook more food at home, as with a commute meals are rushed. Also, happiness level (both of you) will be much higher this way. Focus on what will make for the happiest situation, not the most money. In the long run, that is what matters!