I don't think people get sick more during the holidays, they just talk about it more because they're together so it's easy to say "oh, I was SO sick last week" or whatever. It's true though that it is easier to spread viruses because some people feel this obligation to attend family activities even when sick (I know people who will visit family even when the kids had noro the night before, thus infecting everyone). BUT that being said, it is so much more likely that her stomach hurt for another reason, such as overeating and drinking a bit too much alcohol or coffee! And unless she was v* just before you shared a straw, you're fine. Also, people often say things like that exactly because they are stuffed. I hear it often here, people saying they're so stuffed their stomach hurts and they couldn't eat another bite. I think you'll be just fine!