So sorry about your family’s pet duck. She seems very young to be so sick. I know some about chickens, but not much about ducks, but hopefully others will offer help. The blood from her nostrils sounds odd. ILT a respiratory disease that can cause bloody mucus to be coughed up. Eating something sharp could cause bleeding from the digestive tract. Is there any way she could have gotten hold of rat poison or a poisoned mouse that might make her bleed internally? Giving her fluids with a crop/feeding tube is probably the best thing to do right now to keep her alive. If she tolerates those, you can start feeding some baby bird feed by tube as well. Getting the piece of aquarium tubeing and a regular syringe would be omething you could do today to get started until you can get the proper feeding tube and catheter-tip syringe for later. Here is a simple tube feeding for ducks link to read:
https://www.teediddlydee.com/how-to-tube-feed-sick-ducks/
https://www.teediddlydee.com/how-to-tube-feed-sick-ducks/