Duckling doesn't want to eat and cries all the time
It kinda sounds like she's overly bonded to you as crazy as that sounds. She's become very dependent on you, this is likely because she has no siblings. I raised a mallard drake solo and he acts a lot like this though he does eat on his own which may be because I had to leave everyday so he kinda had to eat by himself or be hungry. If they're raised by themselves they need their mother to give them all the social interaction, the affection, and playing they need to be happy. They also cry and peep all the time so they can insure that they have your full attention at all times. Everything she's doing is to tell you she loves and needs you. The bond ducks form is what a lot of people love in them but being bonded to the point where they won't eat without you is a problem. Try mixing her food with water to make it a mash, this always got mine to eat, and I mean make it almost a liquid. It's hard for ducklings to eat without water and some just can't do it, so making it soupy makes it easier for they to eat. Feed it to her like you fed her now at first then try putting it on the ground in front of her, next to water of course, and see if she'll eat it, keep doing this until she'll eat without you present at all. You can also cut up some greens really small, like really small, and put it in her water so she and see if she'll eat that. You can also mix egg yolk in her water to give her some extra protein, you said she was drinking so this could really help. I remember that crackling sound from when my chicks and ducklings were babies, I never actually thought about it until now though, wonder why they do that. You need to try and make her less dependent on you which may sound weird but it'll be better for both of you. I'm sure you don't want to spend every waking moment of your life with duck crying for you. She can be happy with other ducks and you can relax knowing she's not running around quacking her head off.