You need to provide more details and a real question rather than a title. For now, I'll say this: call 911 and have your parent transported to the ER if you feel there's a medical emergency going on that warrants immediate attention. Your parent can refuse to BE transported, but at least you'll hear what the EMTs have to say as far as her condition and their recommendations are concerned.
I just read your profile. I would assume by your mothers age, you and sister are ar least 60. Is the nephew challenged in some way? How is sister doing after her stroke?
Many elderly people believe that a hospital is where you go to die. It’s what they learned from their parents or grandparents back in the days before medical care became more advanced. If they were to hear about the modern miracles that are performed there, they might be more receptive to going to hospitals.