Please help me out

I really want a chinchilla. I have researched A LOT about them for countless amounts of time. I asked my mom and she said no, because about a month ago I got a dwarf hamster. Since she was saying no because of the close proximity of time between getting both animals, I asked if we could get one this summer or in the fall... But she still said no. So, I looked up many videos and articles on how to convince your parents to let you get a chinchilla and I tried numerous ways (writing a LONG letter, explaining A LOT about them, telling her how much I've learned and know about them, going to the pet store and showing them to her, and even getting my cousin to "test" me on my knowledge of them. Nothing seems to work. She says that we have enough animals but all we have is a hamster and a dog. Is there any ways of convincing parents that you would recomend? I even told her ( which was true) that I have the money to get one and get the cage and that if the money was an issue, we could get one off of Craigslist that comes with some basic necessities and a cage. I also tried to make some deals with her like I could get one if I get straight A's, or do a lot of Chores around the house (which Ive been starting to do more of), and many other things) PLEASE HELP ME OUT!😀😀