I recently became mom's caregiver, she has vascular dementia. How can I help her adjust to her new home with my husband and me?

I transferred here after receiving a call from my youngest sister who shared power of attorney. The other sister that had power of attorney had a nervous breakdown, that developed a phobia of leaving her house. She did for a short while seek medical help and counseling, but then later quit going and treated herself.. then strange things started happening. She became obsessive and constantly taking vitals signs of my mom and determining how long she would live, etc.. Then she became aggressive if we suggested anything different about mom's care. My mom has short term memory, but still is able to most of her activities. My mom would humor her. What triggered the change this sister's daughter had a son recently, and I suggested to find a new apartment without stairs and more room before my mom wouldn't be able to adjust with her illness. This sister did agree, but I later discovered it was because she never thought I could find a place in the small rural town. I did find an opening, a senior built duplex and it took me 6 month's. One of my sister and I took my mom to view it, and she loved it. She even thought the difficult sister would agree. When I called this sister, she reacted aggressive and became threatening and verbally abusive. My mom then didn't want the apartment because she stated we can't make her mad or she won't help me anymore. That made me realize the situation was controlling my mother, this made my other sister's open up about the situation. I asked for my mother's doctor name and number since I didn't have it written down. Called the office the next day, my luck on vacation, I then was given a R.N., I told her why I was calling and the situation. She advise me to contact a social worker on aging to evaluate the situation. I told this sister about the help I contacted. She then took a different turn, started acting pleasant but packed her bags and left! My mom is still able to do most of her routines, just needs someone to make sure she doesn't take her medicine incorrectly and make sure her diet is good. She doesn't want a nursing home. My other sister's and I decided I would take her in. My husband is retired, but works again, and was able to work nights, while I work days. My mom seems to be adjusting well, but I am worried. I bought her a cell phone, printed out new paper work, had it witnessed by family and notarized for me to handle the health. Two other sisters will handle the finances. I know I need to find a doctor for her here. I will talk to mine and her doctor who they would recommend. I set up my guest room with her things. I am going to take the day off work to get organized and find a doctor before something happens..etc any other advice?