This is so sad and breaks my heart. There arent many options, I know 3 things that you can do, 1. take her home with you and care for her until you can get her to the vet. 2- bring her a box of some sort like someone said and make her comfortable or 3 call animal control or a someone who will come pick this baby up and more than likely end its life.
I know that all these options are hard but theres only so much you can do. If you take her in that would be great but you have to think about your other pets nd if she is sick with anything you and your family can catch. If you do not take her in, maybe she should be put to sleep
why have her outside suffering, where some kids or a nasty person can hurt her. I dont know. This whole thing is just to sad, I dont understand why people get pets and just discard them.