Find out the reason for her disapproval. If it is only about taking up responsibility of an animal, then you may convince her with reasons to how you will take care of the issues such as potty training, regular hygiene, family vacations etc. If she does not share your affection for pets, then you must think it through. What happened with us was that me and my brother brought a puppy without my parent's approval. For a few months, I used to wake up once in a while every night to make sure I cleaned up his poop before dad could crib about us not taking care of it. Potty training takes time. But soon we realised hygiene wasn't really what bothered dad. He was very fond of our dog too. He had kept his share of pets when he was young and watching them grow old and die had depressed him so much that he didn't want to go through it again. Mom on the other hand did not like the responsibility, the hair shedding, and the general mess that a big dog can make in the house. And she's not affectionate enough of pets to ignore these issues or deal with them without cribbing.We grew up and left home only to visit home once in a while and our parents are the ones who have to take care of him. He does not get to play as much as he would like and is not allowed in their bedroom. He is happy and taken care of, but it makes me sad that he had to give up on things he loved.So think through. If your parents are not as enthusiastic about pets then maybe you should consider waiting till you are on your own and ready to take the responsibility.