I'm so sorry to hear this and I've been through something very similar with my Dad. I was out of town for a family wedding and left him behind (aged 88 with mild Alzheimer's disease) with someone I trusted. Something went amiss and they called the paramedics and sent him to the hospital alone. When I arrived 4 hours later, he had suffered what we thought was a stroke. He has NO heart or arterial problems. I really believe he was to the point of being scared to death. I won't go on about the lack of care in the ER or the fact that they almost killed him but you can't leave an elderly person alone.
I know that your little one has activities and I know you have a life and I also know that your grandmother probably wouldn't want you to upset your life but if you feel she needs you to be there, I say go. Your daughter will not miss out on anything significant. You can always catch up on school...And you and your grandmother will be better off. I have never left my Dad alone in a hospital. He can't speak for himself anymore and as well meaning as the staff is, everything is standard operating procedure. You are the only one that thinks your grandmother is special.
A., I can tell by the way you are writing that if anything happens to her you are going to take it upon yourself and always wonder if you could do more. Go ahead and do what you can so you won't be at that point EVER. Everyone needs an advocate, whether they are simply elderly or they have a medical problem. My sister and I both have a medical power of attorney for my Dad so we can get all the information we need from the doctors and we can argue FOR him. I know what my Dad wants. The doctors do not.
You have to make this decision. My Dad had been in Hospice Care and the doctors kept telling me (rather arrogantly) that he only had 6 months to live so just make him comfortable. They didn't want me to do anything special for him because that would be too much on me. That was five years ago....
God bless you and you have my prayers.