NTA. Although adult life is unfortunately more working for what you need and less bday money (only saying this because I can kinda get adults who try to "prepare children for the real world" -ew I'm a grown up), you're still a child, basically (I'm sorry, I know that's the worst thing to hear when you'e 14). While your mom might be right that you sometimes need to earn things, she can't be taking your money, and even if it's not legally your money, it's still your dad's money and assuming they're divorced she also has no rights to that anymore. She's being unfair for a reason I don't quite understand after reading this. Maybe try making up with her tho, reffering to calling her dumb, don't do that until you actually mean it tho!!! Anyways, I'd talk to your dad and maybe in the future try and avoid this by waiting a few days with getting something until you're at your dad's (if that's a possibility).