My New Rat Fox Terrior's medical bills

I have just adopted a Rat Fox Terrior. Her name is Bella Luna. I got her as a gift to the family because we are all going through some hard times. We have lost a few people in our family to diseases and have been a little down. I figured an animal with spunk would be a good idea. I payed about $300 for her and got her shots and stuff. She is almost eleven weeks and the worst happened. SHE ALMOST DIED IN MY ARMS. My family is now down once again worrying about little Bella. I took her to the vet because her stool was only blood and she would not move and hardly stayed awake. They told me I had to keep her there for at least 2 days. They said the total would be between $600 and $800. Being a full time student I can't afford to pay such an amount. When I told them this they said I could leave her there for just one day, but that she may die. I could do only that because of my financial standing. I then asked how much and they said $315. I can't believe how much I have to pay for them to just put an iv in her. I don't want her to die because having her stay over night is already killing my little sister. Please if you could help me in any way possible. I just want to give my family that one bit of hope that not everything goes wrong in our lives.