My girlfriend got mad for not buying her Starbucks. What should I do?

My girlfriend (age 16) and I (age 19) have been dating for 1yr and 10 months. Tomorrow is her birthday and so I got her a camera, a teddy bear and made her a card but she doesn't know I got her a present. Today she asked me if I can bring her Starbucks to school and I said yes but after I pick up my brother from school and she said she understood. After I picked up my brother she called and told me if I can take her Starbucks. And I promised her I would take her Starbucks tomorrow. And she kept insisting and she told me that she wished I was different and that she missed the old me since I use to take her Starbucks every week to school. After school, she called me upset and we argued for awhile. We made plans to see each other on her birthday a week ahead;today, because of my actions she cancelled our date and decided to go to the movies with her friends. I told her if I could go with her so I can see her and surprise her with her present. And she said that she doesn't wanna see me but she feels bad saying no so she said yes. I told her that she doesn't have to see me if she doesn't want too. And she told me that she is not like me who says "no" to her for Starbucks. Later, she changed her mind and said that I can't see her tomorrow. She also uninvited me to six flags with her family next Saturday which we made plans for too. I asked her why and she said if I can't spend $4 on Starbucks for her then she doesn't want me spending money on six flags. I told her that money is never a problem. She didn't change her mind and told me im always greedy which is not true. She told me that other guys would buy things for their girlfriends and that i dont. She said not to get mad if she went out with another guy who would do things for her. She said it's my fault that I'm not seeing her. I do wanna see her it's just when I do something that bothers her, she ends up uninviting to dates. It happens all the time and its the reason why we rarely see each other now. Am I wrong? What should I do?
My girlfriend got mad for not buying her Starbucks. What should I do?
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