Mom won't get out of bed, what should we do?

My mom is 94, has lived alone in the house since my dad passed away 4 1/2 years ago. My brother and I went there every evening and called her every afternoon to make sure she was ok and to make dinner. Last Summer she fell two separate times requiring separate hospital stays of a few weeks each time. She broke a bone in her foot one time and the other time hit her head, along with other bruises. She insisted on going home and continuing the same routine. I wanted to place her in a nursing home, where she would be watched 24/7, but my brother was against it. She's gone downhill, forgetting pots on the stove, staying up all night watching TV, unable to deal with bills, only taking sponge baths, etc. A few weeks ago she fell again, on the carpet by her bed. My brother found her and phoned me to help lift her into bed. She's only about 90lbs but I have osteoporosis and arthritis so it was pretty awkward getting her off the floor. I think we should've phoned 911, but she said she wasn't in pain and my brother said he'd stay with her to make sure she was ok. She was shaken up but by the end of  the week she was alot better. About 10 days later she was just starting to use her walker again, when he left the room for a minute to get her something, and he heard a thud. She had fallen from standing by the foot of her bed to the floor. This time someone working in the backyard helped my brother lift her back to bed. Right now (this happened 8 days ago) she's got a badly bruised, swollen upper arm, shoulder, bruised knee. Last night she told me the back of her head also hurts. But maybe that's because she's been lying flat on her back for a week and refuses to get up even to use the commode, we have to use the bedpan. She mostly just goes in her Depends. She said she's afraid to even sit because she may fall again. It's worse everyday, even eating soup flat on her back, her head just on one pillow. I think she should be in hospital. This 2nd fall was 8 days ago and she absolutely refuses to try to get up, she sits up on the bed occasionally, with my brother right beside her. He's been staying there 24/7 since this happened and now I'm worried about him because of the stress and lack of sleep. She won't accept outside help, only wants us to be there. I'm only there every 2nd day now, because of my own health problems. Even though she's 94, she's very stubborn and will not get up. She's got some degree of dementia, takes donnepezil, which I suggested my brother ask the Dr for, about 3 years ago, also she has a pacemaker, takes diuretics, and thyroid meds. I wanted to put her in a nursing home when she came out of hospital last Summer, but my brother felt she'd be happier at home, and she was, until a few weeks ago. I'd really like any advice on what to do now, since we, mainly my brother, do everything for her, and she refuses to get up out of bed. Should we call an ambulance? What should we say is wrong with her, because last time the hospital discharged her last Summer, they said it was because she had recovered and no longer had an a acute condition. Is this refusal to get up and 2 falls in 17 days acute?? I think she should be in hospital.