Teasing is indeed a form of interaction, sometimes involving tickling If a girl is teasing you it usually means she likes you. As far as I know, teasing does not have an exact opposite, however
would all be opposites in action of teasing though not specific to teasing, in the same way
tickling <> not touching
are opposites, though not touching could also be used as an opposite for many other forms of touch
A clear example of the opposite of teasing is an often used admonishment by parents
Child: Daddy, William is teasing me!
Parent: William! Stop teasing Emma and leave her alone!
Parent: William! Stop teasing Emma and be nice!