Possible blockage, maybe hairball + synthetic fibers

My kitten is vomiting and not eating. I took her to the vet yesterday, got an xray that showed nothing, and she ate a little food there so I brought her home. He says her symptoms are consistant with some sort of blockage. The only time she shows discomfort is when she vomits. Mostly what is coming up is clear greenish liquid, no blood that I can see. I started wondering if some mineral oil given by mouth would help move things along. I have no mineral oil but I do have vegetable oil for cooking, and have a small syringe I can use to get it in her mouth. What do you think? She will be headed back to the vet tomorrow if she is no better. She still plays and just sleeps more than usual but I know this can't go on for too many days.