I can't see the moral issue with moving him to a hospice. There may be practical issues (space, media presence etc) but not a moral one. Clearly the relationship with the hospital has broken down.
At least if HD gets this wish, she'll have won something and I think that seems to be very important to her right now. At the end of the day, this a mother watching her son pass away, and I think any kindness that can be offered ought to be, even if she hasn't been rational or kind to the medical staff. She may well regret that later, but right now, I can't imagine what she's going through at the prospect of the next few hours and days.
Peacefulness all round is what's needed now.