I have never previously felt my sister was a threat to my moms well being, but I might have underestimated her.
Yes..much more empowering to do it because of you.
I would also encourage you to shift to "my sister's lack of emotional regulation" is making care for my Mom so much more difficult.
It's hard for me to imagine a scenario where she is granted actual power and can actually make decisions about Mom's care.
So "threat to well being" (maybe a bit much)..."makes a difficult situation almost unbearable" (yep...)
Best,
FF