WHY?!

I have this dream about be pianist. But my mom says that we don't have money for some education or a keyboard I really want.
But I had a plan about some money I got from my mom, grandma and aunt to a Berlin trip with the school. I'll hide some of the money to the keyboard. I told her about my plan and she said NO. Because it was money I got to the trip and not to a stupid instrument.
I was angry. Because it's my dream and I'll implement it.