Thank you all for your lovely and supportive comments. They were wonderfully helpful and heartwarming. I hope I will respond to them more personally but until then, please know they were appreciated.
My mom is feeling pretty much back to normal now and is awaiting results of her biopsy. Originally we thought we would hear tomorrow, now it sounds like we are hoping for the day after tomorrow.
My brother gave up his heroic act after three nights and fled back to his own apartment. I think he will be easier to deal with now.
I asked my mom to please stay with my brother for the night before their consult at Mass General so they can both see what it feels like for her to be staying there, since he had said she could stay with him while receiving treatment. She responded that she's planning to do so... but she already thinks it won't be a good idea to be dependent on him.
So now she's moved on to Plan C, based on the advice of a good friend and neighbor of hers, which is to go to the Lahey Clinic in Boston. This friend of hers works there and she has several other friends that work there as well. This way, she could rely on friends to help her get there if she can't drive herself, rather than only relying on my brother.
I'm very, very relieved that it seems like we won't have any family drama for the time being.
Oh, and this neighbor also told her that bladder cancer has an excellent prognosis! So that's excellent news!