I would recommend traveling with a mask if she's coughing/sniffling frequently. I know it's embarrassing to wear one, but at the very least, she'll look like a courteous traveler. Even if she's not contagious due to antibiotics, wear the mask just to show people that you're doing your best to stop the germs from coming their way. I think it's the least that sick people can do when traveling and might keep someone from being rude to her when she feels terrible.