Cat with *extreme* social anxiety

[Zoneseek]

Hi all, figured I would post this here and see if anyone has ever run into this kind of thing before.

My girlfriend and I recently moved in together. She has 2 cats, I like cats and my family had a cat when I was younger. One of her cats is perfectly normal, the other one is mentally screwed, to put it lightly. It is a seal pointed ragdoll, with the most extreme social anxiety I have ever seen in a domesticated animal.

The cat absolutely hates to be seen by anyone other then her and will refuse to come out from under the bed if anyone other then she is in the house. The cat will come out to eat/drink and use the litter box once a day, otherwise will never leave from under the bed. He would do the same thing when ANYONE came to her apartment where she used to live, but it would only be for a few hours while people were there, so it wasn't anything to be concerned about. Now that I am around basically whenever she is around, noone ever sees this cat, its under the bed the whole time anyone is in the house and refuses to come out, to the point of hissing and clawing the carpet if she tries and brings him out.

Some other points of history with this cat would be when he had fits of panic when the bed wasn't there because of moving twice in the past, and once he even jumped off a 35ft high deck because he didn't know who was opening the door TO the deck.

I personally think this cat is the most ridiculous animal I have ever seen, but she loves him so what can you do. She got him from a breeder who kept all her cats locked up together and away from humans so they were never socialized properly, but this is just insane. She noticed something was wrong right when he was a kitten and she brought him home, and he wouldn't come out for days at a time. Personally I would have taken him back for my money, what a waste, but shes not that kind of person.

Any ideas what can be done? Its only been two weeks and its driving me nuts hearing about it non-stop and having to feed a ball of hair that noone ever sees.

Thanks in advance for your help.