Legal Question in Family Law in Montana

I'm sorry that your sister didn't discuss her plans with her daughter. I assume daughter was surprised, disappointed, and maybe a little insulted that perhaps mother thought daughter wasn't up to the task. Or perhaps mother realized daughter wasn't emotionally mature enough to handle the task. Being PR can be very difficult when one is also trying to maintain one's own life in the days following a death.

Montana may but is not required to grant a third party a "parental interest" in the child if

1 - the biological parent has 'engaged in conduct' that is contrary to the parent-child relationship, and

2 - the nonparent established a parent-child relationship with the child, and

3 - continuing that relationship is in the child's best interest.

Otherwise, parents have the right to limit relatives' time with their child. If this is a recent problem, you might try achknowledging daughter's surprise and disappointment at not being named (assuming it really is a surprise and a disappointment), commenting on it being more work than you imagined, etc. She might be under the misunderstanding that being the PR grants power to distribute the estate as you please, or she might worry that some treasured items will be overlooked.