Sadly, I agree, it does sound like she's not well and he wanted to get rid of her.Smell her breath when you feel of her crop, to see if it has a sour or bad odor. She may have sour crop or be suffering from a yeast (fungal) infection. That can be hard to treat. She also may have other underlying problems, such as a reproductive infection or internal laying. Your dad’s friend just sounds like he was dumping a sick chicken. I would check her crop every morning to see if it was. Emptying overnight. Get some miconazole or Nystatin cream from your pharmacy and give some according to this article:
https://www.backyardchickens.com/ar...w-to-know-which-one-youre-dealing-with.73607/
She also may have a lowered tail, so check for a full lower belly between her legs. Has she laid an egg since she has been there? I would check her for lice and mites on her skin, as WR recommended, and consider worming her with Valbazen or SafeGuard Liquid Goat Wormer.
I would treat the crop as suggested, consider deworming and do look her over for lice/mites.
Hopefully these symptoms can be resolved, but keep in mind that there may be something else going on with her.