SW at rehab told me Fri .that Medicare wants to discharge my 91+yr old mom this Wed. after 9 days. Mom wants to return to her condo. Oh no!

She is basically bedbound with severe hip pain due to advanced osteoarthritis (with broken hip 3 years ago). Yesterday I found out that she is no longer agreeing to be taken to the bathroom because of the pain, which still exists even though for the last 10 days she's been on daily meloxicam + Tramadol (PRN, but she's asking for it every 6 hrs). She's in rehab again after being transported to the ER 10 days ago for severe hip pain. Another extensive workup in the ER (including CT) showed: nothing. She is at her baseline for everything. Per her ortho doc, she is not a candidate for surgery or any more cortisone injections.
This time the hospital didn't admit her, but kept her over the weekend for observation, because she wasn't safe to go home. This exact thing happened in late April, she went to rehab, returned to her condo in May, spent weeks with in-home PT. A month after she finished PT, here we go again. Before this episode, she had been prescribed Tramadol PRN, but up until now was unwilling to take any pain med regularly due to a fear of worsening her kidney function (& possibly dying young, I guess).
She is now on a total of 11 medications. I asked for a palliative doctor to see her in the hospital; this is the dr. that prescribed the pain meds she's currently being given. This doctor said my mother absolutely should not return to her condo; she needs to be in a facility. She predicted my mom will be right back in the ER if she returns home.
Currently, my mother has CNAs coming in the mornings M-F. She had refused to have anyone on the weekends or the evenings. Her mobility has declined precipitiously over the last year. She has been getting around her condo by sitting in her rollator & being pushed by an aide, or pushing herself with her feet when no aide was present. She does not have the ability to use a wheelchair, and it would be difficult for anyone to manuever one in her crowded condo. I think that PT is fruitless at this point.
Her first care meeting for this stay is scheduled at the rehab tomorrow; I already told the SW that mom absolutely cannot go home on Wed, as I can't get aides rescheduled by the agency that quickly. I don't feel that she should be going home at all. She cannot take care of herself. We are fortunate that she has the means to pay for 24/7 in-home care, but the reality is that it is very difficult to manage it (we have done this for shorter periods before). My mother's regular aides have all missed work this summer due to health problems of their own, & the aides that have been sent for the overnight shifts in the past are not wonderful. My mother is now showing evidence of cognitive decline. But she is adamant that she will not go to a facility - she thinks that she's refusing AL, however I think her needs are too great for AL - she's now a nursing home candidate. The palliative care doctor wrote in her notes that she did not feel my mother is at the point where the health care POA should be invoked.
My brother said that my mother is going to do what she's going to do, and we should just let her go home. He has stopped visiting/calling her (it's been a long 9 years) and I don't think he understands how poor her condition is. I'm SO sick of this, but in good conscience don't feel I can throw up my hands and walk away.
I could sure use some advice.