What can you do after you tell your good friend who is a girl that you like her as more than a friend and she said she just wants to be friends but now acts like she doesn't?

Relax, be patient, don't crowd her, or push her. You have probably scared her, because she does not want to get into a physical relationship right now with you. Let her have her space, but don't start treating her like you don't like her anymore. Don't call her up every day, when you don't have anything to talk about, don't follow her around. Spend time with other people, do things by yourself, take a step back from the whole thing. You have not done anything wrong, so don't start feeling guilty or ashamed. Try to be the way that you were when you first met her.