My father asking me to buy something - my sister bothering me about it

My father keeps asking me to buy him something when he can just buy it himself. He lives in upstate NY and I live in the city. Today he asked me to buy him some jars of natural honey because he can't find anywhere in the stores near him. However, he then told me that he found some online. Now my sister is asking me to buy him more jars of the honey anyway even though he already bought. And she keeps bothering me about it.

Is it wrong that I told my sister that he can buy it himself online? I'm not trying to be selfish or anything. Keep in mind that I live very far away from him and it would be very expensive to mail glass jars, and they're perishable. And why should I buy something for him if he already had bought it online?