Legal Question in Elder Law in California

To obtain formal authority as a Guardian, you'll have to file a Petition in the local Probate Court. That is a detailed, technical, and somewhat costly process, and necessary only if she has assets in her name like real property and bank accounts that you have to have court approval to control, or if the home won't allow you as next of kin to handle her arrangements. Talk to the home and check the assets before jumping into filing. Then if you determine you need to hire counsel for this, feel free to contact me.

If your Mother has legal "capacity", then you may want to try getting a power of attorney for financial and health care decisions. That would give you legal authority to make decisions over medical care and to access her accounts and property. As the prior answer notes, it depends on what sort of assets your mother has and what you need to do to manage those assets effectively.