Cats fighting

Question
I have three cats: Colby(8 yrs old, male, neutered at 4 months), Jesse (6 yrs old, male, neutered at 4 months) and Lucy (1.5 yrs old, female, spayed at 3 months). I have had all them since they were 6-8 weeks old. Colby and Jesse have always gotten along well with only occasional play fighting or minor tiffs.

Jesse is skittish, shy but very sweet. He was not at all pleased when I brought Lucy into the house and he has never really accepted her. In the beginning, she would want to play with him and smell him out but he would swat at her, hiss, and yowl any time she came near. I have recently moved from a house with a yard to a two bedroom apt. They used to be able to go outside and had a lot more space and since I've had to move the aggression with Jesse and Lucy has escalated. Lucy seems to attack Jesse just to torment him. She hears him in the litter box and hides outside the door to jump on him when he comes out, she stands on the coffee table and jumps on him when he walks by, she jumps on him when he's resting, etc. I don't know how to get her to leave him alone and how to get him to accept her. I bothers me because Jesse freaks out so much that he often throws himself into furniture and other things. They aren't particularly rough with each other when they make contact, Jesse just makes a lot of loud yowls and hisses but I worry that he's going to hurt himself by accidently hitting furniture. How can I get them to settle down with each other?

Answer
If you are around usually when she attacks, you could try something that I have done with my cats; whenever I could tell that something was about to happen, I would toss a loud noisy toy across from the way so that my cat would have to run across the room to get it and completely distract her from my other cat. It simply gave her another option instead of tormenting my other cat. They still do have their tiffs, but definitely not as much as they used to. You could also try making a noise that scares her, also as a distraction method. I really do have full faith in types of distraction.

Let me know how this goes and see if we need to do a different approach.