She sounds so little--5.6 lbs. isn't much for a cat. But at least she's in a reasonably safe place for the next three days.
When you get back, if you can you might want to look into getting a specialist. E.g., we have an emergency animal hospital here with specialists in internal med, gastro, and cancer. They found a solution to a problem one of our cats had that almost killed her. So just a thought...maybe you can ask your vet if he/she knows some specialists.
"My predominant feeling is one of gratitude. I have loved and been loved;I have been given much and I have given something in return...Above all, I have been a sentient being, a thinking animal, on this beautiful planet, and that in itself has been an enormous privilege and an adventure." O. Sacks