I'm really sorry about your cat. But not at all surprised that Ethel noticed your grief and comforted you. Feel free to say what she did, if/when you wish.
SO glad that she has begun to eat on her own. She won't overeat on regular chicken feed, but could overeat scratch grains, bird seed, etc. if offered free-choice. Which could cause her to become overweight, and you Definitely don't want that. Plus, scratch and birdseed don't provide proper nutrition that a chicken needs. In the video where she put her beak in the water bowl but didn't lift her head, and when she was pecking the floor around her, I think she was hoping to find more delicious bird seed morsels! Overall, she looks more animated with every video you post, which is Great to see.
What were you offering her as far as food that she wouldn't eat on her own? The best long-term feed for her going forward is All-Flock chicken feed. (Or maybe non-medicated Starter/Grower chick feed.) Both come in crumbles form, which she will likely find more enticing than pellets. If you add enough water to the crumbles to make them clump but not become mushy, that will usually entice a chicken to eat. The way I do it to get their attention is set the food bowl in front of them, make sure they are looking at bowl, pour water in bowl (which also gets their attention), then push the mixture into clumps with my finger, which will usually entice them to eat. It's ok to mix some scratch or bird seeds into the wet chicken feed if she won't eat the crumbles by itself, but asap try to get her eating regular chicken feed.
Is she still frequently adjusting her crop that
@Wyorp Rock commented on? It crossed my mind that possibly the plastic tubing had somehow irritated her crop. Tube-feeding is usually only needed short-term, so if she will eat on her own that is best, but she still needs her vitamins.
I'm tagging
@azygous @Wyorp Rock @coach723 to address your questions plus add anything else they think you should know. I'm pretty certain she won't overfill her crop in one meal, so until you hear from others let her eat a fair amount. The main issue is the scratch doesn't provide proper nutrition that she needs. But in addition to all-flock chicken feed, i think she also needs her vitamins. You should hear from a tagged someone soon.