How can I get Mom proven incompetent?

My other sister has POA but the evil one does not allow us around and prevents us from knowing anything Yes, she has admitted to using debit cards and checks being written for unknown reason. Yes I have talked to police over the drug dealings this person does and otherwise they view this as a civil matter. Police were called and told I had to be removed for mom's protection. HAHA accused me f shoving mom. I'm a few yrs older than 60 and never shoved my mother in my life. Just simply the way mom talks, her unusal words, her reversal of her normal feelings, making ridiculous statements, like my 20 yr veteran son doesn't know what he is talking about when he said there was a shotgun shell in the chamber of a gun.She accuses me of spending all my money at a casino. I haven't been to one since I took her about 6 yrss ago. Accused me of blowing all my husbands inheritance. Sorry folks no inheritance there. No I have not been allowed to see her in 7 months, according to the sister, she the sister must protect mom. I ask mom about it, she claims the last time, I never said that. they're saying that.

Were you thrown off the property? What was that about?

Does someone have Power of Attorney? Guardianship? Medical Power of Attorney?

How do you know that your mother has become incompetent? If you can't show up at the house, do you see her often? If you get your mother declared incompetent (which is done by a court, on advice from physicians) what do you intend to do?

Do you have evidence that your sister is stealing? Did you present the evidence to Elder Abuse? Is the evidence clear enough to present to the police?

I am sincerely sorry that there is conflict among you siblings. That always adds stress to an already stressful situation. Please provide a little more background information so we can respond to your specific situation.