It could be the cold, could be teeth or she could be having too much solids.
If you are offering water with solids she is unlikely to get dehydrated, but obviously keep an eye on nappy output.
If it the cold or teething it should pick up gain in a couple of days, if it doesn't I would scale solids right back until it does and then gradually increase the solids again. It's quite common for milk to drop with a bit too much solids at this age.
Laura