If one parent opens up a bank acct in their Childs name can the other parent try to freeze the acct?

Hi I am divorced and their is a child born of the marriage.. I had a separate party for my child and the money she got i wanted to open up a bank account in her name and put money in her account... If I did that is there any possibility that my ex can get access to the account? We have joint custody but she's residential. Can she have her lawyer try and freeze the account or is there anything she can do do cause a problem?she's very money hungry and I've had issues with her for years and I want to make sure she can do nothing and can't gain any access at all to the account. Any knowledge would be so very appreciated. Thank you