Can my sister who is my moms power of attorney keep me from visiting her?

My mom is in a locked unit for dementia. She frequently doesnt get fresh water or her pills are left at the bedside. I have voiced my concerns many times with the staff and called the state dept of health many times. today when I expressed my concerns the staff called my sister who has her poa and they stated they would call the authorities and have me removed? can she do that?