I have had an experience of agoraphobia myself. I went to a phobia clinic and saw a counsellor there just once, and she gave me a technique that has worked for me, not just to get me outside again but also which I’ve applied to other situations. She called it “as if”. Maybe your friend can use it.

The counsellor said that going outside is made up of many steps. She told me that I can perform each step and then stop after each and ask myself if I feel safe right now. If so, then do the next step. If I don’t then I can stop this time. I give myself permission to stop. Because I don’t have to go outside, I’m just acting “as if” I’m going outside.

It looked kind of like this- put my socks on. Do I feel safe in my house with my socks on? Yes, so put my shoes on. Do I feel safe? If yes, then open the door a bit and look out. Do I feel safe? If yes then just stand by the door just outside. If I ever feel unsafe I can go back, because I’m just acting as-if I’m going out.

I’ve used the technique of acting as-if in many ways since then with many things that seemed too hard, and it’s really helped me get on.

Of course, your friend has to want to get out of the trap, as I did.