Sheryl, I am very sorry for what you are having to deal with. I'm not sure what Jan is thinking--what her motivations are. We had a similar situation with my grandmother. Luckily, I was the POA. Dealing with nursing homes is absolutely exhausting. My brothers and sisters and I were fortunately on the same page, but that didn't prevent the nursing home from doing what they wanted. One of us was there every day and information from the nursing home was always in question. I know drugs are needed in some cases, but this was ridiculous. I finally had enough--I told my brothers and sisters I was moving her into my home (my husband was wonderful about it) and hiring a live in nurse. While that was difficult, I certainly am very glad that I did what I did. In the long run, it was easier to keep an eye on things, and it was definitely better for grandmother. I am sure that it extended her life and definitely she had a better quality life.
Now, all that being said, my suggestion is to get some legal help. Does Michigan have a social services department for senior citizens that you could contact for help? Could you report the nursing home for abuse? Could you somehow talk with your sister Jan and tell her that you know that it has been hard for her to take on this burden and that you and your sister Pam would like to help her. Somehow make nice (even though it would be difficult) and maybe get a joint POA where you and your sister Pam would have more say so and get her moved to another nursing facility that you have checked out and approve of and maybe even move her closer to you. Maybe your sister Jan would go along with that--maybe she is getting tired of the "fight". When you are looking for a lawyer to help you, make sure you find one that is conversant with geriatric law. Also, and this is the biggie--is there any way you could take your mother in until you can find a place that you think would be good for her? It sounds like there is a power struggle on Jan's part and she is not really getting the seriousness of these drugs that are being given to your mother. Sometimes, it is the combination of drugs that causes the combativeness in older people. Good luck to you and let us know how things are going. You and your mother are in my prayers.
I just read the previous posts--the ones above this one that were posted while I was writing this one and Debbie's advice is excellent. I'm glad she knows where you can start. Good Luck and God Bless.