Why Is My Cat Being So Aggressive?

So, first of, I have 3 animals. A dog named Euro, and two cats named Harley and Tinkerbell. Euro and Tinkerbell are fixed, but Harley was not. (We are getting her fixed today, but when everything happened she was still in heat.) My cat Tinkerbell has been acting very.. aggressive lately. Just so you know, she is very spoiled, bratty, prissy, and hates when I give another animal more attention than her. (She is a very jealous cat.) But she isn't aggressive. Maybe when she was little, she would swat at me a little. But now, she's an all cuddle cat. But just the other day, I heard very loud fighting and it was bad. At first, I thought maybe it was Euro and Harley. But Harley was hiding in my bed whinning. Euro and Tinkerbell were fighting and they knocked the printer over. Now, anytime Euro comes near me or Tinkerbell, she hisses at him and tries to swat at him. They're both okay, but she isn't the same.. I don't know what's wrong. She has that black goo in her eye, even though I thry to whip it away. And she's been throwing up her food lately. Can anyone help? I have no idea what's wrong with her.