Hello Jo.
As a former sufferer from a generalized anxiety state, I can vouch that Reiki has virtually eliminated the problem.
I found that full body treatments helped me considerably and, as holobon rightly said, if nothing else, induce a state of relaxation, which helps the healing process.
I also found that the practice of Reiki helped me enormously and, although the problem can still rear it's ugly head, I find that I can control it by self-Reiki.
Unfortunately, it seems that a general anxiety state has no specific cause which can be isolated and dealt with so the only option appears to be some form of relaxation therapy.
Keep it up, it is the best thing you can do for your friend.
Beannacht leat,
Brian.