This word makes part of the Dutch local dialects, and means as described above "tappen". What it means when a girl calls you like that, I do not know. In which part of the Netherlands or Flanders did you hear this ?
You should have included the pronunciation. I wonder if the word "taboo" were meant, especially since that word is also spelled "tapu." If you were a foreigner in the Netherlands, this would make some sense if the girl believed that she should not date foreigners, for example.