how do I change a will or trust when all of the inheritance was left to my minor child by her deceased father and I am not executor?

My ex husband died and left our only daughter (13 yo) his estate through a will. He named his sister as executor and stipulated in the will that our daughter would inherit the money when she turned 25 yo. He never paid any child support or helped me with any support to raise her when we divorced. Now that he has passed, there is a significant amount of money that his sister has control over for my daughter. When probate clears, she will be starting a trust for my daughter and she will be guardian of the trust. She is a little off balance and a very controlling woman who regards my daughter as her own. I would like to know if there is any way to contest the will Or trust so that I have control over or at least access to my daughters inheritance to use for her and our family while she is growing up.