I may be getting a new cat on Monday. I currently have a seven year old Seal Point Himalayan named Kira and a 2 1/2 year old yorkie named Lacy. My boss has neighbors that recently had a baby, and now they want to rehome their cat because it keeps trying to lay on the baby. I don't really understand why they can't think of a problem to the solution because I know two different women that recently had babies and each have three cats! But anyway, she's also a Himalayan..a flame or cream point, and my boss is bringing her to work on Monday for me to see her. She's up to date on vaccinations, spayed, and declawed. They said she's a nice cat but a little shy. That's all I know about her now. I feel terrible that she's being rehomed but I'm excited about seeing her on Monday.
It sounds like you're going to have a lot on your plate. Since your new cat is shy already, I would make sure she has a place in your house away from the other two animals, hopefully a whole room. That way they can all explore the others' smells through the door before they come face to face. Take it slowly and you will a much happier new kitty.