A) Have her see a gastroentologist (sp?) I had the same problem for a while (not quite so extreme, but close) and getting on acid reflux medicine took care of it for the most part.
B) If the gastro doesn't pan out, Have her see an endocrinologist. There are many other internal conditions (including thyroid and autoimmune disorders) that can cause difficulty in swallowing.
C) She may want to check with an allergist as well. Did she have any other reaction when she choked? Could it have been an allergic reaction?
D) And as mentioned, it could just be fear at this point that is keeping her from being able to swallow. I've been there, and though I rarely have trouble any more, I still can not eat or take pills unless I have 2 big gulps worth of a drink handy.
E) Tell her if she starts to choke again, one of the most important things she can do is to RELAX. If she doesn't panic immediately, she may be able to force her throat to relax enough for her to finish swallowing. This has helped me several times before as well.