If you find out, let me know.
There are darn few "qualified" experts on adult diagnosis (although being 20 is close enough that the "raw material" is there to diagnose as if she was still a teenager). I've been trying to track down someone in my area, and with no luck.
I can tell you that your best bet is to search in major metropolitan areas (New York City, Chicago, Boston, LA, San Francisco, Dallas, etc.). If you can find just one expert, they may know who else in the country can do the job and refer you.
Heck, I tracked down someone listed as being an expert in Tennessee only to have them tell me they weren't set up to do the job.