Filing/opposing Guardianship of parents. Any advice?

it's now over a year later, after my mother's sudden TBI which left her incapacitated, my sister filed for guardianship of both my parents. My father has parkinsons and alzheimers, is doing relatively ok and looks for my mother everyday, it's a sad and tragic situation that I cry anytime I have to write or talk about it in details. Regarding my mother, I have a "flawed" DPOA which lists me for certain things and me and my sister for medical. I say "flawed" because I asked a friend/lawyer to look it over several months later and he said it wasn't perfectly written but that it would hold weight if ever this went to court. Some siblings had a fit when they found out about this document which has never been used. On top of threatening to take me to court (some of them were downright nasty while I was in the middle of a high risk pregnancy during this time), they said it wasn't my mother's signature which the lawyer said that it wouldn't matter even if I signed for her because she was present -- document is notarized. During the past year, me and 5 siblings met a few times to try and resolve matters. We agreed to me and her doing co-guardianship but a week later, one brother was against the idea. I decided to take myself out of the guardianship plan because as a new mother of twins, my stress level was through the roof. A different brother and the same sister were going to do co-guardianship but the same brother opposed this plan too with personal attacks against the other brother, etc. The brother who opposes everything has serious issues and was out of state at the time. A close family friend offered to do guardianship with my sister to help out the sibling drama and once again, that brother opposed that plan too. He only wants her to do it because he knows he can manipulate her any which way. Fast forward to now, she has filed on her own for full guardianship of both parents. There have been enough examples in the recent past which demonstrate that she is not only easily influenced by others (including the evil brother who wants everything his way only), but also not upfront about things and not trustworthy (again based on what has happened over the past year). In the end, she wants to make the final decision, however, I'm seriously struggling with all of it because some decisions will be regarding their end of life care and financial matters. Probably the main reason for filing is that she wants to sign off on an out of the country property sale. If she becomes the guardian, are whatever properties including items in the home, automatically owned by her?? I hate to be cynical but I can foresee lots of issues because she has such animosity towards me and another sibling in particular.
I know my mother wouldn't want this whole thing to be as painful as it is for her children (an amazing mother/human being) which is exactly why I can't in my right mind, allow certain people (who are not trustworthy) to "take over" and then at that point, I really will have no say. I just truly think that 2 people need to co-guardianship, how will the Judge (in NJ by the way) see it?? So I will be filing opposing her being solo guardian, I also need to include a statement, how far back should I go?? talk about who did what before the accident or just recent examples?? She has a lawyer that filed for her, I don't need one but would like one. Any and all comments are greatly appreciated....