Most of Mom's assets are in a revokable trust, and she has become angry at one daughter and wants the other one to become the trustee. She also wants to change who inherits from the trust, and what percentage each gets in order to punish the one she is angry with. I know that a lot depends on the language in the original documents creating the trust, but has anyone had experience with this? I have heard that in general the legal burden on changes to a trust are not as high as for changing a will. On example is that she was sole trustee originally but when all 4 daughters plus her doctor simply wrote a letter saying she was no longer able to safely manage her financial affairs, her designated successor went in place. No other proof was needed.
In addition, it does sound as though your mother might be experiencing a temporary hostility toward the one daughter. If this is reversed, then changes might have to be made again.
Any maker of a revocable trust can change it by virtue of a restatement or amendment, if that person is of sound mind. I honestly don't know how changes could be made though if any dementia is involved. That's definitely an issue for an attorney.
I'm not sure what issues there would be that a "burden" for a trust change is not as high as that for a will. Codicils to wills can easily be made. Actually changing a trust would probably require changing the pour-over will too, as well as any certificate of trust existence and authority.
Maybe I'm missing something in the interpretation though.
The trust must have provided specifically for automatic authority switch to the designated successor if lack of financial responsibility (or other conditions) were specified. However, I'm a bit curious to whom this letter was directed, as your mother as settlor/maker of the trust would have theoretically been the one to whom such a letter was addressed.
There really are 2 unknowns and possible complications in this situation:
1. Whether your mother has any dementia, and
2. The scope of the guardianship order and what powers were created, and that's not an answer that anyone can provide without knowing the scope. You might want to reread it carefully to determine if there is anything in the Order that speaks to your mother's authority to effect changes to legal documents.