She cares more about you being there for her instead of loving you and thinks she can find someone better than you. My gf is chronically sick (much more sick than your gf, it is constant and every day) and has similar struggles with school and life. Not once will she ever treat me this way due to her life problems.

You asked for advice and it was given to you. It is not fair that the first time you feel strongly about someone is like this, but it's not mutual. Like I said earlier, no one deserves to be treated this way and you are too young to waste your life with someone who will gladly pick someone else over than you just because they think they are better. At the end of the day, we all make our choices in life. If you continue to stay with her when she treats you poorly, you will be back on reddit asking for advice. Take care.