Was Victoria her best buddy? Chickens definitely make friendships and bond with other chickens, and grieve when one dies. Even those not "best friends" with a member of a group that dies will be "off" for some days after. At the very least the absence changes the dynamics within the flock and...
So @TwoCrows suggested a calcium supplement, and I would agree, because it won't hurt her in the short term and might help. I give two hens here calcium citrate which is more readily absorbable than calcium carbonate and it helps their eggshells. Since not everyone needs the calcium boost I give...
Maybe she'd like to be inside with you, where it will be warmer if it's cold out. If she hasn't eaten much it will be harder for her to feel warm. Could it be possible she ate what Victoria did and is feeling poisoned, but she just didn't eat as much maybe? You could try some sugar water or...