Thank you for contacting JustAnswer.com with your question. I will provide legal information related to your question.
Her lawyer is wrong. The evidence required is "what is in the best interest of the child" and do you have a relationship with the child that is now being prevented?
Here is the Montana law. Basically you will have to file suit to get visitation, it is not an automatic right.
Except as provided in subsection (5), the district court may grant to a grandparent of a child reasonable rights to contact with the child, including but not limited to rights regarding a child who is the subject of, or as to whom a disposition has been made during, an administrative or court proceeding under Title 41 or this title. The department of public health and human services must be given notice of a petition for grandparent-grandchild contact regarding a child who is the subject of, or as to whom a disposition has been made during, an administrative or court proceeding under Title 41 or this title.
Grandparent-grandchild contact granted under this section may be granted only upon a finding by the court, after a hearing, that the contact would be in the best interest of the child.
A person may not petition the court under this section more often than once every 2 years unless there has been a significant change in the circumstances of:
(1) the child;
(2) the child's parent, guardian, or custodian; or
(3) the child's grandparent.
The court may appoint an attorney to represent the interests of a child with respect to grandparent-grandchild contact when the interests are not adequately represented by the parties to the proceeding.
This section does not apply if the child has been adopted by a person other than a stepparent or a grandparent. Grandparent-grandchild contact granted under this section terminates upon the adoption of the child by a person other than a stepparent or a grandparent.
Title 40, Chap. 9, Part 1, §40-9-102