AITA for not allowing my sister to rent a room in my house?

My sister(28) has been struggling for years with finding a decent place to live. She currently lives in an apartment that is basically falling apart. I(30m) was really proud of myself for saving up for so long and getting a nice house. It's not huge but it's in a safe neighborhood and the house is basically in new condition. Now, I know it may seem AHish that I'm not letting my sister move in but hear me out.<br><br>My sister has never been good about paying bills or rent on time. She is not lazy and has a job, however she constantly spends her money on useless stuff. She has thousands of dollars worth of comic books that she never touches. About 15 years ago when she was living with our parents, she spent almost all of her money on fidget spinners. It was almost to the point of hoarding. <br><br>Early this year she asked if she could rent the extra room in my house. I told her that I wasn't comfortable with letting her move in because of her past. She asked me how long I was going to hold this grudge for. I was taken aback by this because I don't feel like I'm holding a grudge. I'm proud of myself for saving up for this house. I don't want to risk losing it because she can't pay the rent. I told her this and she got angry. She said that I'm being a selfish bastard and I have an obligation to help her out. I don't see it that way.