Alex, Well I just can't stay away from a good old fashioned sex talk, so here is my opinion. I do not feel anything that can be compared to an erection. When I am horny, I feel like Mojo and experience a tingling or warm sensation. Also I have the jumpy and "on edge" feeling..just the physical sensation of needing release.
Where I DO feel a definite physical change is in the vagina. It literally opens up like a flower when I am thinking about sex, anticipating sex, and of course when I am about to have sex.
For me, the erection of the clitoris happens AFTER stimulation starts. Sometimes I can feel myself enlarge in H's mouth, or under his fingers but I hardly ever feel that in the absence of direct stimulation. Whew! I know you didn't mean this to be a hot thread but it sure is making me ready for bedtime.
If your fiance experiences orgasms, then I'd say that her problem is in the desire department, as opposed to the physical malfunction department. Not WANTING an orgasm and being unable to have one are two different things, kwim?
Hope you get it all figured out soon and BEFORE the wedding!