Silkie is not a good choice as they are particularly susceptible to Marek's. I'm not sure getting a new bird would be a good idea anyway. They would be at risk and could also bring disease/infection with them and your Marek's bird is vulnerable to infection due to a likely compromised immune system and if she dies, you are then left with a single "alien" hen to try to integrate into your flock. That would be a lot of extra stress for no real gain.
Hope you can keep her interest in food and she can turn the corner with this.
Hope you can keep her interest in food and she can turn the corner with this.