what is fallacy:when someone ask reverse question, in answer to question asked on first place and avoid answering that question

for example in some conservative culture , going to movie theater or bar or pub or naked girls dance is unacceptable ,
so people will go to those places by hiding themselves from their relatives ,if they found each other they feel anxious
sara and jhon are brother and sister and they both go to same bar and they eventually find themselves
the conversation b/w both of them go like this :
jhon : sara, what are you doing here ?
sara : what if i asked you the same question ?
jhon : silence..

what would be logical answer jhon can gave to his sister ? what fallacy it have? and also consider the scenario