My Mother presented to an attorney after being diagnosed with end stage cancer to create a will and passed away before signing it.

I was named her health care proxy and power of attorney while she was alive.On the day that we went to have the Power of Attorney signed she expressed that she wanted a will and I was to receive everything.The attorney asked her if that was her wishes and she said yes.There was an appointment to return in order to sign the will but My mother became ill and was hospitalized .She was unable to make it back to the attorney's office to sign the prepared will because she passed away.She made no provisions for my sibling and The Attorney gave me a letter stating this fact and I need to know how to enforce her wishes because I would like to exclude My sibling from gaining any portions of her estate as per her wishes.Is an officer of the Courts a " witness" ? Can I ask a judge to make no provisions based on The facts enclosed?