Question about a shared parenting plan.?

My ex-wife and I have a shared parenting plan with our 4 year old daughter. I am her residential parent when I have her and she is when she has her. As a matter of fact here if a direct quote from my attorney about decision making. "With shared parenting, it is umed that the two of you will make the decision jointly. Since you cannot, you then turn to any provision in the paperwork which allocates decision-making authority. Since there is none, I would advise you that the two of you are on equal footing." Now for my question. I have her Sat.-Tue. one week, Sat.-Wed the next week. When her mother picked her up tonight she told me that she has enrolled her in a pre-school Mon-Thurs. 8-noon and I am suppose to take her when I have her. I have told her from the start I am not taking her to a pre-school when I have her. There is nothing saying I have to & if I am able to make her decisions when I have her I don't feel her mother can tell me what to do when I have her. Any advice?