If you are yelling at her, you are not disciplining her. Discipline is what your daughter requires. Regarding the crying, my question is how much of your attention do you give her when she cries? The best thing to do when you daughter cries after being told no is not to give her any of your attention. If you starve the attention, she will find it useless to unproductive to cry. Only provide her with your attention when see behaves appropriately. Yelling at her when she cries is like oxygen to a fire - it will simply grow out of control.
If she can feed her self, why are you feeding her? If she chooses not to eat in defiance, then she simply doesn't eat. You should not be feeding her. Trust me when I say that she will not starve to death. She will simply eat when she is hungry. However, she should only eat during meal times. If she is defiant during a meal, she simply goes without until the next meal time. Soon enough, her defiance at meal time when disappear!
Yep, Mark is right. You say NO and she starts crying put her in a timeout and tell her that when she stops crying she can come out. She will go nuts for awhile. Let her cry. The change will not happen overnight as she has learned how to get your attention and it will take several weeks to change that behavior, but it will change. You might want to get the book - "SOS Help for Parents," by Lynn Clark, to see how this system works.
thanks im taking her to see a nutritionist specialist to see what can be done to help her eat better.