Would it be messed up if I got rid of this cat?

So long story short, I rescued a cat from a terrible fate, and brought her home with me. She's been with me for a couple of days. We have a pretty good bond. I'll be honest, I don't want a cat, because they cost a lot of money to care for, and I'd rather spend money on myself. I was planning on taking the cat to the no kill shelter. The cat was very aggressive with the previous owner, and his family. It looked at a mirror and whent crazy. That's what I told the humane society, and they said that if in a week the cat hasn't showed any aggressive behavior then we can talk. She hissed when my dog got too close once, and she saw herself in the mirror and started attacking it. Also, if the humane society doesn't wanna take her, then I was gonna rehome her to someone else. Would that be wrong?

Would it be messed up if I got rid of this cat?
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