A bit of cooked pork and cracked corn as @Ribh mentions would be a good choice for a few days. What the corn provides is easy burn carbohydrates and that provides calories to help keep her warm.
The pork will provide a complete protein but even more important, it is apparently easier to digest than a complete protein provided by mixed grains.
There you go, @Aussie-Chookmum, Shad's provided the science!

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Will sardines do any good? I don't have cracked corn or pork at the moment but I will keep it in mind. Thank you both for your advice.
We did a shopping trip today and although I didn't find cracked corn, I found live crickets!
The girls had a very exciting time chasing them around the run.
Except Alice.
Alice ran away

Before I adopted chickens I had no idea about moulting or how feathers grow back. I'm finding it a fascinating and worrying process.
Alice's feathers are coming in apace. She looked even more like a porcupine today. It looks painful too.

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And a closeup to see how they come in. (in a thumbnail for the squeamish)
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Sardines are fine in the short term and very good for them. The problem is with the tinned ones is the high levels of oil and salt. If you are prepared to feed them fresh cooked sardines they are better than pork, but here they are very expensive.
Chickens seem to be much like humans in that they like a lot of stuff that isn't really very good for them. They will eat high carbohydrate and heavily flavored foods all day from what I've seen.