I have 8 siblings, but I alone, am my mom's caregiver, 24 hours a day, 7 days a week, morning till next morning, because either my sister don't give her meds and she is anxious and can't sleep or she gives her a bunch and I'm up changing her urine soaked clothes cuz she cant make it to the bathroom. She can't even walk for that matter and checking her breathing, because shes so doped up! I feed, bathe, and everything else, while my sis is so kind to stop home to give her idk what kind of pills, push her around and scream at her for following her around, and then back out for a busy day of spending my moms money. Oh I forgot she does take her on nice car rides,but not to her appointments or anything, but to sign papers for whatever she wants in her name, how caring. So I did call APS, and SSI, and anyone who will listen and help her. And I will not leave my mom, until she dies from natural causes or otherwise. I will fight for her till someone helps her and stops my sister!!
A guardian is assigned by the courts and needs to prove that the person they are trying to get guardianship over is incompetent to make decisions.
If your sister is guardian the state makes her account for Moms money. She reports to them.
POA is assigned by the principle. If sister has POA then there should be paperwork. Not sure you can request an accting of how she spends Moms money may need to consult with a lawyer.
Social Security money should be used on Mom. SS very strict about this.
You mentioned you've already called APS and SSI and I'm assuming you didn't get anywhere with them.
Can you get your mom to the ER and upon check in, tell them it isn't safe for her to go home and talk to the hospital social worker so she can get you the proper help/resources you might need?