Help with cats who don't get along

Hi, I own two cats, and they don't get along, and I could use some help.  

Here's the story. We've owned Willow, a 6 year old spayed female, since she was a kitten and she was our only cat. She's kind of shy and passive and, except from my wife and me, gets very frightened and aggressive around other people and animals. About 6 months ago, a friend had a cat that they had to give away, and we decided to adopt Bella, who is another spayed female of the same age. Bella is the exact opposite in personality - outgoing and friendly. The cats seemed to tolerate each other for a little while as they just left each other alone, but after Bella got used to her new environment, her nature pretty much made life very stressful for Willow, and there were several little scuffles which Willow tended to lose (being passive in nature, plus a little but smaller). Eventually, Bella gained the run of the house, while Willow pretty much holed up in our kitchen, hiding in the cabinets. We did our best to keep Bella out of there and gave them separate food and litterboxes, but eventually we decided to take Willow and isolate her in our bedroom (the only room in our apartment with a door).  She's been in there for a week and she has really calmed down to her old self, but we don't really want to keep our cats separated and our bedroom door closed for the next 10 years.  We want to get Willow and Bella to, if not get along, at least be able to stay in the same room together without a war starting.

I've read a few things about introducing cats, but I'm not sure if it will work this much later, plus just putting the cats near each other sets Willow into a growling fit.  The vet recommended some pheromone spray, but I'm kind of skeptical about it, and I would have no idea how to use it properly, plus it's kind of expensive.  Willow seems to have accepted the "smell" of the other cat - we use towels and the like on both cats with no issues, it's the sight of her that gives her problems. The cats have no other behavior problems, and aside from fleas (they're being treated) are in good health, though Willow has lost significant weight due to her stress (we're trying to fatten her back up). 

Any advice would be appreciated.

You can do the whole introduction process, and people often do.  It doesn't matter that they've been together for a while.

You really need to be patient and do it 'by the book' though.  Here's an article that describes the process: http://www.thecatsite.com/a/introducing-cats-to-cats

Also, pheromone spray (Feliway is probably the best known) can be excellent.  Some people have no luck with it but others absolutely swear by it.  I have the spray and use it in times of stress and it works wonders with my two.

Welcome to TCS!!

Thanks for the reply. I did look over the "introducing cats" thing, and I'm positive that they're used to each other's scents by now.  Attempting a meeting just causes Willow to growl and try and run off. I'll give that blanket thing a shot.

As for the pheromone spray, how exactly would I use it in this situation? Would I just spray it around the room beforehand? Spray the cats themselves?

The introduction process goes well beyond just having them smell each others scents.  The process usually takes a few weeks to a few months.  It all depends on the cats temperaments.  You also need to be the judge as how quickly or slowly to move depending on what you witness.  If you are seeing growling or hissing, chasing or body language signs such as ears back and tails swishing then you need to slow things down.  Some steps can take weeks.  If you rush the process you will end up having to restart.  I had to restart and it then took months.  Here are a few more links as well as a video.

http://www.catbehaviorassociates.com/a-simple-little-trick-to-use-during-new-cat-introductions/

http://www.aspca.org/pet-care/virtual-pet-behaviorist/cat-behavior/introducing-your-cat-new-cat

http://jacksongalaxy.com/2010/10/01/cat-to-cat-introductions/

So they've been separated, and the older cat is actually very calm for the most part. The spray seems to be working (I overused it, though. Ineed to get more), and I also got her a catnip pouch that seems to have really mellowed her out (the newer cat doesn't respond to catnip). I put both of their food dishes right by the door. I've been moving a cat bed between the two cats, and while the newer cat willingly sleeps on it, the older one will stay on it but not go onto it by herself that I've seen. I've also caught them sniffing and scratching at the door at each other, but when I opened the door to see what would happen, the older cat just gave a quick hiss and a slow retreat. So I guess that's progress.  

My big concerns right now are, first, when I'm ready to introduce them, how do I actually do it? Do I just put them in a room together and watch?  Also, it's a bit unrelated, but I want to keep both the cats out of our kitchen, and we have no door. The one time the older cat got out of the bedroom, she ran right back to the kitchen and tried to get into our cabinets again.  The newer cat doesn't go in there at all anymore.  Is there any way I can keep them from wanting to go where they're not wanted?