Are you keeping them inside now?

I know it's hard, especially when one cat feels very protective of his/her territory! I have brought two cats together before, though. Start out with both in separate rooms for a week or so. They will still be able to smell eachothers presence, but the new guy will be able to explore without being harassed by the other one. Then, try letting Jimmy (cute name, by the way!) out for a little bit each day. They WILL fight at first! Then put Jimmy away again for the rest of the day. Gradually increase the amount of time they are in the same room. They may never like eachother, but generally, they learn to live with eachother eventually. It IS frustrating! Good luck and keep us posted.

I assume you have vaccinated Yin already.

As far as the two getting along together, you hit the nail on the head. your house is Yins temple. It will take time for her to become comfortable with this intruder. From what you have said about Jimmy, he has no problems with Yin ruling the house, so things should settle withen a few weeks to a month and a half for the most part. The main trouble is that Yin has an established territory (all of your house) and Jimmy has none. Probably Jimmy will, if he hasnt already, stake out a spare room or a closet and slowly he will be tolerated in other parts of the house by Yin.

Unfortunately, the only real answer is time and patience, and a squirt from a water bottle if things get too heated. The same thing happened when I moved in with my wife before we married. She had 2 cats and I had one.

Let Yin know she hasnt been replaced, and let Jimmie know that this house is his home as well, and slowly things should get better.