Declining medical care is your choice, just make it an informed one, not a zombified one.
I was horrified a while back when my brother went in for minor surgery. He's an elder, but something of a moron. He's never been very "book smart" and couldn't explain to you the JW blood doctrine without reading word for word from the Society's literature. He had no idea that what blood fractions even are, much less which are and are not permitted. I'm not even joking!
I saw him take the newly-revised folded blood card with medical directive included and check off that he would not accept ANY conscience-optional blood fractions or procedures! He did this without giving it any thought. His idea was simply that "Jehovah hates blood, so I'm not accepting any of it." Thank goodness he came out okay and this was never an issue. How would he explain to his two children that he chose to die over accepting medical procedures that weren't even banned outright by his church leaders!
I had to sit back and politely try to talk him out of it, but he was having none of it.
Another question: If a JW was taking care of a non JW and the JW didn't allow the non JW to get a blood transfusion, would the JW leadership support the JW?
This is what an power of attorney for medical reasons (called a medical proxy in some places) is for. If you live in the U.S., you can sign one and appoint a person you trust to make medical decisions for you in case you are unable to. It's exactly what the dubs use to ensure that someone is there to prevent the doctors from conducting a blood transfusion. You can use the same document to ensure that there is someone there to make sure doctors take whatever measures are available to save your life. If you're over the age of 18, I suggest you execute one. Your mother would have no say over your healthcare decisions if you have one in place.