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I am sorry to hear about your mother's situation. As her guardian, you will be able to override her decisions, make decisions for her, and get her the help she needs. It would be as though she was a minor. You'd file a petition with the court, serve all interested parties, and have a hearing. The Court will appoint you in the best interest of the ward, if the Judge agrees to this. You'd have to serve all immediate relatives, the aunt included, and they can decide not to become involved, or reply and support or not support the petition, and possibly introduce another candidate for guardianship such as themselves. The judge makes the final decision.
For more, see HERE.
Counsel is recommended but not mandatory. The main form for the petition for guardianship may be found HERE. But this is only a part of a complicated process that can take months to be finished.
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