Unbalanced chicken...

Hi,
I have a cochin/silkie cross that is nearly a year old. We got back from a weekend away to find her stuck sitting outside in the run. We live in Norway so it's cold outside....mostly below freezing. The poor girl was very cold and shivering and unable to stand. We brought her in and kept her a couple of days in the warm and after she heated up again she was able to stand and move around, but she keeps over balancing and falling forwards. It seems to be always that she overbalances forwards. Other than that I can't see any other symptoms except that she absolutely stinks. We've had to move her out into the garage because she smells too much to be indoors. She seems quite good in herself and is eating and drinking. Because we were away for a couple of days I can't say whether the problem came due to her getting cold or whether she got stuck outside because it happened (more likely I think), but I know she seemed perfectly healthy before we left. I can't find anything on the internet that describes this.

Does anyone have any ideas?