"I have been told that the court...." Told by whom?
If you were to go to court to petition for a name change, and it came out that you deliberately went against the father's wishes and attempted to informally change the child's name, you would risk the judge inferring that you are trying to alienate the child from her father, and that you don't respect the court's authority and orders. That's not a good position to be in when you go to court, when you're trying to convince the court that the name change is in the child's best interest.
As you note, you have not changed your own name yet. You have the option of maintaining a "name link" by continuing to use your married name. I understand why you would like to revert to your maiden name, but changing your child's name is not a decision you get to make unilaterally, nor is breaking your child's "name link" with her father.

