<human>: Hey,

So for the past couple of years my little sister has been obsessing over the idea of getting a pet dog. My parents dislike animals (mess, trouble, $$, etc.) and have been denying her, which results in arguments with her and crying sprees which annoys us all. 

My parents don't want to be troubled with taking care of a pet, and although my sister promises that she can take care of it by herself, she has shown repeatedly in the past that she simply can not handle the responsibility of having a pet. She is still too young. Her previous "pet" rabbit was left in the basement alone, ignored by her and fed only by my mother before we gave him away, and it is the same with the lizard we have now. 

I would have no problem helping her take care of a dog, but I cannot since University + Co-op means I will never be home, unless I get a co-op job in my home town, which is unreliable. 

So we need to convince her to end this obsession. My parents have tried reasoning with her, but since she is young and naive it isn't very effective. 

What is a good way to end this obsession and avoid the tantrums?

Can you give me a shortened version of the text?
<bot>: Sister obsessively wants a pet dog, parents deny. How do we end her obsession without her going crazy on us?