keeping play piano if she does not like to quit

we never companied my kids when they were playing their piano. I expected them to finish all of assignments when I came back home from work. My job is to check their homework from school and chinese homework from me. I never checked their piano since I do not know anything about music. My daughter was very bored of playing piano when she passed level 7. she did not like to quit when I have asked her. I dare not to enter her teacher's home because it was ashamed of hearing her teacher to criticize her. She only practiced half of hour before she went to her piano class every week when she was last two year of her piano lesson. you can imagine how furious her teacher was.
She won some awards when she began to play piano and was always on the honor list with her syllabus. I did not know how she managed to pass her last several levels before she finished her final level 10. My husband has said that you could hear angriness from her playing. I was glad with that I did not stop her piano class. She really enjoys to play piano when she did not need to take a class. now She can play it several hours in the weekend. my boys never won any award. so I let them play the "half-hour" they called. the half-hour includes drinking water and going to bathroom. so what? they do not make a living by playing piano. it is for fun, isn't it? do not be too harsh to you and you kids.