@Null, I would bring attention to how it makes other people react/feel. Eg. "I know you like talking to other people and being friendly to other people. Sometimes, you stand too close to people. When you hug or kiss someone without asking, they will be surprised, or scared, or uncomfortable, or angry. It is not polite to stand too close to people without asking. Other people do not like it when you are too close. Other people do not like being touched if you don't ask first. If you want to touch someone, you must ask for permission. You must ask for permission every time you want to do a different touch. Other people like talking to you when you respect their personal space.
If you touch without asking and getting permission, people might report you to other cons and other cons will ban you because they think you might do it again. They do not like it when you touch other people without permission. Some people like saying hello to you but do not like being touched."
Of course, you can't guarantee that Christine won't slip up again. There will always be an unpredictability. Christine will need regular reminders, especially before cons, and I would say someone to stick with her and keep an eye on her during the day.