So she has feelings for you but school is important to her and then you argued that point with her, wanting it your way yes?
Apologise to her would be my first step, sounds as if you argued and then quit talking properly and she's irritated maybe, because she finally spoke and it ended in non-understanding of her needs and led to an argument.
That's not the fairy tale she would have expected, having admitting she had feelings for you..
Remember, relationships are nurtured. Both parties are important. Compromise is part and parcel. And all a girl wants when she gains feelings is to dream, smile, be happy - not argue and lastly, it does appear that school is important to her and that's a good thing...
Maybe suggest after you apologise that you hang out on Sundays, support her in her decision to concentrate with school and tell her that you are proud of that and she is going to go places in life. Let the rest fall in together. Patience.