Trying to get more Time.

I have a four year old little girl who loves coming over and seeing me and her brothers and the rest of her family on my side and wife's side who has been in my daughter's since birth. When my daughter gets dropped off she runs to me smiling and laughing. You can tell she's happy. When she gets picked up though it's literally the polar opposite. She tries to hide, she cries and screams that she doesn't wanna go back with her mommy. I know she is only 4 but she's very vocal about where she wants to be and that she doesn't wanna go back. I'm not looking to take her away from her mother at all. I know she loves our daughter. I just more time with her we currently have an agreement that I have her Tues. At 11am to Wednesday at 630pm and every other weekend. She refused to even give me an extra day when we went to mediation. Even the mediator asked why since they found no reason why it would be an issue. Her exact words were I'd rather have a hearing. Is there anything I can do to help me make my case and get me more time?