Should I return my new kitty to the Humane Society?

[awkwardsilence]

A lot of the time, she is the nicest, sweetest little kitty and she cuddles and plays nice, but then sometimes she gets this evil look in her eye and attacks you. I noticed it one of the very first days we had her, I had to lock her back in the bathroom for the night, and when I picked her up, she meowed an evil meow and tried to bite and scratch me. I've never been able to pick her up without being afraid. Another time, I was petting her on my lap and all of a sudden she bit me, I blew in her face to scare her away, and instead, she launched her whole body at my arm and started attacking it. Yesterday, I was walking away from her, and my husband said she looked like she was going to pounce, sure enough, she launched her whole body at me and clawed onto my backside and held there with both claws. Surprisingly, she hasn't really hurt anyone yet, but I'm so scared that she will. If that's not enough. I've barely seen my old cat Twilight since the new cat Luna got here, because any chance she gets, Luna attacks her, Twilight always surrenders, but that doesn't stop Luna.

I have grown to really like this cat, but I am also scared of her a lot of the time, and I just don't think we can retrain a cat who is this mean. She's a year old, and I think the behavior is so ingrained in her that she'll never change. It makes me extremely sad that we will likely have to take her back, but I don't know what else to do. Help?