Does a person usually have to be deemed incompetent to get POA?

I didn't realize you live with and care for your Mom when I answered first time, though you did make that clear. As your Mom has been deemed COMPETENT by APS she can change you to being POA any time she would like to. This would require a lawyer visiting your home if Mom cannot get out to do this work. Just ask Mom is she would prefer you to do the POA. If she does, then get the new POA for financial and health care done, and visit the bank with same. This will mean Sister doesn't have access to account. You can also become your Mother's representative payee of Social Security benefits. This requires careful record keeping for your yearly report to SS. Look up on the Social Security Website. Good luck. Apologies for not knowing that your Mom is in your full time care. Are you paid by your mother for any of this care? If not, perhaps this is something you should discuss with the Sister. You cold always leave the sister with ALL of it, the care, the finances, and etc., move out and begin to have a real life. The bickering over Mom and her Social Security check will eventually get old for you both, unless it has been something ongoing for some time.

You have to be deemed COMPETENT to give a POA to another. What that means is that you understand what you are doing. You need not be perfect. That is you can have long or short term memory deficits to some degree, but the lawyer examining you while the papers are done must be able to examine you to the extent that he can vouch that you understand fully what you are doing in making out these forms, and that you are fully informed.

I think after all your postings here, HesterSue, it is clear to all of us that you don't wish your sister to be caring for your mother. But in fact she is. She have reported her to APS and they have said that there is no case.
Your sister is providing care for your mother. It would be good now if you would lend support. Apologize to your Sister and be there for her, helping with Mom's care in any way you can. THIS will put you on the scene, something that you were NOT, I assume, when APS visited. I don't know where you got the information that the sister answered for Mom. APS almost always interviews the Senior and the person accused separately so that the senior can say what they wish. You cannot have been there, yet you tell us this was not done.
I also very much doubt, as you were not there, that you have any idea what documents they saw. If your Mother is indeed competent, then she can make you the POA any time she wishes to.
It is my feeling that you will soon be utterly unwelcome in the home of your Sister. I do know if I were caring for my parent, trying to provide all they need and doing financial and medical POA work as well as 24/7 care that you would not be welcome in MY home.
We cannot know your Sister's side of things. We DO know that you have done what legally you are able to do, because you have told us so, and told us that APS has told you there is no case here.
Sibling wars tear aging elders in half. It is like being drawn and quartered when you are too old and weak to fight back. It is a weak spot for me, so forgive me if, on this your third or fouth posting, I seem cranky. There quite honestly is nothing anyone on the forum can do but tell you that we are sorry for your pain. And I am.

I don’t know what state your mom is in, they don’t all do it exactly the same way but a basic POA simply gives someone the ability to act on your behalf, at your direction when it comes to legal documents, typically financial business. Some give temporary or narrow ability to say act as your agent on a real estate transaction and some like the ones we typically refer to here give broader ability to take care of any financial business AT THE DIRECTION of the person granting that legal ability so your mom in this case but it does not give that person the legal right to act without the agreement or a actually direction of the primary (your mom). A DPOA (it can have variable names and some stars they are the same document unless specified otherwise) is what kicks in when someone is deemed “incompetent” or unable to make decisions for themselves and enables the appointed person to make decisions, in the primary’s best interest, for them. These durable or jumping POA’s usually have requirements that need to be met for them to kick in that include at least one doctor committing to paper that the primary is no longer able to make decisions for themselves and can include requirements that multiple doctors or people agree they are no longer competent. Guardianship is similar in the end function but it is awarded through the court system (I believe even when the primary grants it) so another legal process and the guardian then has to report to the court regularly and account for all monies spent and decisions made. Because a DPOA does give the holder greater responsibility and freedom to carry it out it seems to me it also opens them up for more scrutiny so records should be kept well and if other family members have serious questions about how things are being handled APS and or the courts are more likely to listen. Remember acting solely as POA assumes the primary is competent and approving the action so if it isn’t the primary making the complaint (all they need to do really is revoke the POA) the waters are a bit different than when the primary has been deemed incompetent, at least from a legal perspective.

So the answer to your question is multiple people can hold a POA for one person and even for multiple purposes, the only thing that makes it kick in is that it is signed notarized and exists. However if you are talking about a DPOA or jumping POA then yes the person has to be deemed officially incompetent by whatever requirements are set in the document. Now to further confuse things there are also MPOA (medical power of attorney) and health care proxies which cover medical care not financial business. As your mother’s primary caregiver it’s a little surprising you don’t have any of these things, are you the one that takes her to doctors appointments? If so perhaps they have you on record at least as medical proxy or granted access on HIPPA paperwork on which case you should be able to discuss her medical situation and living situation with her doctors who should help if indeed she needs care she isn’t getting or is in danger. I’m also curious why you leave your mom alone with your sister if your mom is so afraid of her and mom lives with you. I mean your sister has to come to Moms residence which is also yours to visit, care for, see mom so while it isn’t ideal you could just make sure you are always present, right?

If you wait for incompetence then you would need to pursue guardianship. Very expensive. Reading your threads I don't see how you came to be mom's caregiver. Does mom want that? More importantly, do you?

If your nother is competent, then she can change POA to you.

That is the simplest solution I can think of.

my friend is going through the same ting you are... it seems crazy.. and she called me to ask if I could look at the hospital her mom was at,, etc.. her sibling got poa for some reason.. the whole family sounds like they are concerned but cannot do anything to get mom into a good place away from their sibling. mind you, mom has 6 kids.. one bad apple got her... and the othera are not able or scared the apple will sue.. for what reason?