Encountered a pathetic and ill mannered lady (50 something female) in sarojini

So. I recently got transferred to delhi for my govt job. Not that this is my first time in delhi. Was here earlier as well for my upsc preps. I went to sarojini on sunday to buy some dresses for my sister and niece who is 4 yo. i went alone in the early morning to avoid crowds. I wasn't sure about the size of a sweater which i thought of buying for my niece. so, there was this woman (around 50 ) just besides me. i very politely asked her in hindi " excuse me aunty, yeh sweater ka size 4 saal ke bachche ke liye theek rahega kya ". She made a very disgusting n irritated face and said in a very bad way "I dont 'have any idea. ask the owner. i am not the owner here " in a rude way. and then after a pause of 2 secs, uttered "uncle" . Did I do any wrong by asking her this? Are all delhiites (middle class specially) are this rude? Seriously.. i am disappointed by her coldness and rudeness like she behaved as if I harassed her or something however, not surprised keeping in view things i have heard about delhi from people n friends and the kind of news that i encounter about this city.