MOm has alzheimers and recently ordered something over the phone that was costly and she didn't need- she is 86 and it was anti-wrinkle treatment system. She later tried to cancel it but couldn't get through and neither could I so we were just going to send it back when it came. Instead, she opened it, not remembering now that she had ordered it-swearing she didn't order it. Now she wants to move into a smaller duplex in the same area we live in to save $100.00 a month in rent, not realizing how much it will cost to move her and she will have to move again at some point when she no longer can stay alone. We were going to move in together, she forgot all about that and changes every day what she is going to do. The other part of the equasion is that I have a sister that is here also that I am sure puts ideas in mom's head but denies it to me. From her (the sister) history she can't be believed. She is extremely jealous of the relationship I have with Mom and I know she takes any opportunity she can to try to come between us because Mom has told me things that the sister has said that were either not true or non of her business to tell. I feel like I am going crazy, trying to help Mom and trying to make sure the sister isn't working with me. She know I have the power of attorney and I know that she is very mad about that. She acts so nice, but she never misses an opportunity to go behind my back and undermine any plans Mom and I have talked about.
About the contention with your sister: It is very common that siblings have some sort of tension between them in these situations. When it's our parents well-being, we're dealing with, a lot of emotions come into play. Recognize that and come to a meeting of the minds with her (and any other siblings). Agree to share with each other whatever conversations each of you has had with your Mom. Second-hand information can be dangerously misleading. It will be best for your Mom if you two are united and there is a minimum of stressful contention.
If you are the person named in all the legal documents, and you have authority to act, then you can take the lead. I recommend discussing your decisions with your sister beforehand, and where possible, meet with her and your Mom regularly to discuss what's going on. Keeping things out in the open will be healthiest for everyone. A book to read and share is: "They're My Parents Too" by Francine Russo.