I agree with granny but to take it further and not knowing your age or financial status, you need to let her know you will take full responsibily for the project, first handle it like a business, keep a financial statement showing all cost , cost of calf, feed, medicine,ect. write a contract between you and mamma that all monies she invests will be repaid with interest at the time of sale. Open a bank account for your projects only, if you make a profit it will be invested in next years project , keep doing this yearly until you have made enough profit to finance your own project. By doing this you will have money to help pay for your college education, or help you go in business when you get out of school,prove to your mother you are responsible and have set yourself a goal using the money from the projects, not blowing it on something frivilous.
No matter what your age when you start a project ,( here the youngest is nine year old) you need to take full responsibilty of raising the project that means feeding in morning and evening , train the animal as it should perform at the sale, ect. the only time the parents should be envolved is for advice , support and transporting not daily maintenance. One of many pet peeves I have is the parents that raise the project and the kids just stand back and watch then taking the money for the project and blowing it.