I am an adult convert and I did not get slapped during Confirmation, nor did anyone else, male or female.
I have never heard of such a tradition, and would be shocked to see it, honestly. I do hope that, if our bishop plans to slap our teens at confirmation, that we would be warned beforehand. And I hope that it is not a painful or humiliating thing.
That just seems strange to me, considering the scandal the Church has gone through. In my experience, the priests and bishops seem very concerned with avoiding any hint of impropriety, and a slap, whether forceful or affectionate or whatever, seems very improper. I am very curious to see what other people say about their experiences, or those of the teens of their parish.