kimbrey,
Your understanding of the situation is basically correct. Essentially, if you want to be a practicing dermatologist, you need to redo residency here and getting a spot would be next to impossible.
If you wanted to do an intern year and then practice dermatology you could do that in some states. Of course, no one reputable would hire you, so you would have to start your own practice and you couldn't claim to be a board certified dermatologist. You may also have great difficulty getting on many insurance plans, so actually getting paid for seeing patients may be difficult. However, in most states you can get a medical license after internship, so it would not be illegal to do this. I think this is a bad idea though.
There are rumblings about changing this requirement that you redo residency because of an anticipated shortage of physicians in the US, but no one knows if or when this will happen.
The only reasonable thing that I think you could try is to approach academic programs. I have heard of them being able to get you some sort of licence where you could practice in some sort academic setting doing clinical research. But every state has different requirements, so it may be impossible in certain states. Also it would require that the program knew about all the hoops to jump through and was willing to do all of that work. Furthermore, the salary would likely be very low (compared to other derms) because they know that it would be very difficult for you to just leave and work somewhere else. It is likely that the British dermatologist that you heard of is did something like this.
In the end, I think it is safe to say that while this move may be awesome for your fiance's career, it will essentially destroy yours. Only the two of you can decide if that trade-off is worth it. It is undoubtedly a horrible situation to deal with.
Edit: I just remembered another thing you could do. You could contact pharmaceutical companies and try to get some sort of research position. Of course, you wouldn't really be practicing dermatology, but you could at least do some work in the field and get compensated for it. Of course if you really enjoy practicing clinical dermatology, the such a position is unlikely to appeal to you.