Good to see you de-cloak, UberTanker. How have things been since March?
I'm a conservator for my Dad's finances. For the state of Colorado, that's just an annual report to the probate court listing assets, debts, and expenses. My impression is that the judge only gets involved if a report is not filed. Otherwise my brother and I handle Dad's expenses as we deem prudent, and we let the state (and Dad's care facility) know if Medicaid will be necessary.
Depending on how your sister's trust is set up, you may be added a trustee with signature authority for checks or online accounts. I doubt you'd even have to deal with government supervision. It's probably more important that the rest of your family be kept informed of how your sister and the trust are doing so that they don't feel left out.
The book written on E-R.org, "The Military Guide to Financial Independence and Retirement", on sale now! For more info see "About Me" in my profile.
I don't spend much time here anymore, so please send me a PM. Thanks.