I have to say that I don't think you can punish your child for what happens at daycare. You have to work with the daycare to find a discipline that they can impliment at the time the bad behavior is occurring.
I have this exact problem with my 4 year old when he is at Grandma's house while I work. I can not control what he does when I'm not there. At home he naps like a champ or at least plays quietly in his room for 1 1/2 hours. We have never had a problem at home. However, he will not remain in his room at Grandma's and does not go to sleep. I feel this is because Grandma has not disciplined him at other times so she is unable to control him at nap time.
Hopefully you can work with the daycare on this to find a solution. I'm sure she isn't the first one to have this problem, but the daycare can not put this responsibility on you. It's up to them to take control of the situation. I know it must hurt you to hear that your daughter isn't behaving when you're not there. It's a difficult situation to be in. Good Luck!