With the information provided, there is absolutely no way any of us can make an intelligent diagnosis. The entire DDx for vomiting is possible. Chances are it was either motion sickness or related to her cancer, but we cant possibly know that.
This is no business for germophobes who cant control their issue. you will come in contact with sick people every day. If you cant wash your hands and move on with your day, I would suggest another line of work. If you're going to stress out every time a patient coughs, sneezes, vomits, or bleeds on you, you're going to be a nervous wreck in a week.