If you and your sister don't agree with Mom's decision, split your inheritances with the excluded sister after Mom's gone. The attorney works for Mom, not you and your sisters.
If you believe Mom is not competent, you need a letter from two doctors stating that, or the lawyer is using his best judgment (which, granted, is not that of a doctor and may not be the greatest).
My experience with my parents' attorney is that he was extremely diligent about my parents' trust and their decisions about it. My mom was in the early stages of dementia when they set it up, but he did feel that my father was completely fine (he was) and had my mother best interests at heart, plus Dad fully trusted me to be the Successor Trustee and hold POA for them. In fact, three years later when Dad was the one to become terminally ill before Mom, it was the attorney who suggested that they both resign from the trust and allow me to take over the finances before either of them died. Mom was deeper into dementia but not totally out of it, but he had no qualms about letting her sign because Dad was still completely competent. The important thing was that I, as the POA and Successor Trustee, had absolutely nothing to do with those decisions and the attorney didn't feel there was any coercion.
I would think the important piece would be if your mom understands the implications of making such a change and why she wishes to do it. The lawyer should be interviewing her privately so there is no undue pressure during the process. That's what my aunt's elder law attorney did when she made a change.
First, since it's apparently not your sister's trust, she has no right or standing to opine on what or who can or can't be included or excluded.
Second, I'm not sure an attorney would rely on a standardized test to determine capacity. He/she's the one making the determination on changing a trust, not a doctor. And the issues and questions are vastly different.
Are you opposed to this change, and why? It really is your mother's choice, isn't it?
If you believe Mom is not competent, you need a letter from two doctors stating that, or the lawyer is using his best judgment (which, granted, is not that of a doctor and may not be the greatest).
My experience with my parents' attorney is that he was extremely diligent about my parents' trust and their decisions about it. My mom was in the early stages of dementia when they set it up, but he did feel that my father was completely fine (he was) and had my mother best interests at heart, plus Dad fully trusted me to be the Successor Trustee and hold POA for them. In fact, three years later when Dad was the one to become terminally ill before Mom, it was the attorney who suggested that they both resign from the trust and allow me to take over the finances before either of them died. Mom was deeper into dementia but not totally out of it, but he had no qualms about letting her sign because Dad was still completely competent. The important thing was that I, as the POA and Successor Trustee, had absolutely nothing to do with those decisions and the attorney didn't feel there was any coercion.
Second, I'm not sure an attorney would rely on a standardized test to determine capacity. He/she's the one making the determination on changing a trust, not a doctor. And the issues and questions are vastly different.
Are you opposed to this change, and why? It really is your mother's choice, isn't it?