My horse is lame in a back leg. Should I call vet, ice, or wait?

Poor Gigi! If she is non-weightbearing on the affected leg, I would recommend calling out an equine vet right away for an emergency visit, as this is often a sign of a serious injury such as a fracture. If she is bearing weight and acting normal otherwise, you could try stall rest for the next few days with lots of soft bedding to see if the lameness resolves. You can certainly try icing or cold-hosing the hoof, but it's hard to say if this will be helpful or not without knowing what is causing the lameness. If there is no improvement in the next 3-5 days, or if she isn't eating or having any other symptoms, she needs to be seen by a vet right away to find out what's wrong. Your vet can take x-rays or do other testing if needed to help diagnose the problem and see what can be done to treat it.