"Tu" is indeed the second person singular, but in French, the plural, "vous" is used unless you are familiar with the person. Since I don't really know Twister, it's somewhat impolite to use "tu", unless she prefers that I do. Someone significantly older than myself could use the "tu" form without being considered impolite, and teenagers/children can also use it with anyone their age or younger (at least in Québec).
Is the distinction strictly singular/plural in Italian?