The symptoms you describe, I would lean toward your pullet having Marek's, but there's really no way to know unless she passes and you get a necropsy.I read a month, although sometimes it can be quick, but vit B complex is needed. Ours only was handfed the first week or so but then could eat fine if supported in a sitting vertical or an upright position. She just does not balance well, but eats great now. Don't give up yet
Vitamin therapy shouldn't be used long term.
I agree it is up to the individual keeper how long they want to continue to hand feed and/or offer supportive care to a sick bird.
A lot depends on their goals and what they suspect the bird may be ill from. If you are wanting to breed forward, then sick birds should not be bred, imho. You would also need to consider whether the bird is shedding a virus or has something that's contagious and can be passed to the flock.
I hope you see improvement soon, keep us posted.