I'd check her crop and feel of her abdomen below the vent between her legs for any signs of bloat or a feeling of fluid.
When you lift her/carry her, don't press on the breast/crop and make sure her abdomen (below the vent) is supported very well.
Try not to carry her often.
I would suspect she may have some reproductive problems going on.
Could be a crop problem, but anytime I've had a hen begin to show distress when being picked up/held or carried, they had a reproductive issue, usually accompanied by the symptom Ascites (fluid in the abdomen).  Sometimes fluid can be drained to make a hen more comfortable for a period of time depending on the condition that's causing the fluid to accumulate.
I would still give the vitamins and Calcium as suggested.   Possible she is having troubles expelling lash material or soft shelled egg.  This can cause some limping or trouble with mobility if there's pressure on the nerve.
Try to encourage her to eat her normal feed.  While it's always a pleasure to see one eat when not well, she does need a nutritionally complete diet to help with healing and overall health.  
If you do have Vet Care available, it may be a good idea to have her seen.