"Sometimes its really hard to differentiate between her symptoms and normal sickness."
I am glad to hear that she is feeling better. This sentence really struck a cord with me because I think even as an adult with this disease for more than two decades, I have trouble determining whether the onset of symptoms are the return of crohn's vs. a normal illness.
I struggle to find a balance between not just dismissing a symptom as crohn's and also not just dismissing it as something else.
"S does eat food now but because she is small and underweight she has to get a boost with tube feedings at night. Because she is underweight, I sometimes feel almost desperate at the dinner table to get her eat (which probably isn't helping)."
From what I understand, this is common. Our son's speech(feeding) therapist advised us to try to make the meal experience as positive as possible. To try to mask our frustration, desperation, etc, as best we could, so that our son didn't associate eating time as a tense situation. A LOT easier said than done, but you think of a game plan ahead of time, realize/accept that a lot of it is going to fail, and it help me have a little better, calmer frame of mind for the whole feeding process.
With respect to the tube feedings, are they prescribed before bed as 1 feeding, or as a continuous thing overnight? When we got to the point of weening off the tube feedings, we were advised to try to time the tube feedings with a normal eating time. Supplement what was not eaten during a meal with some liquid in the tube. That way the brain will associate eating with feeling full.
Good luck at the Mayo Clinic. Hopefully they will confirm your first opinion approach or advise you towards something else that will also work out really well for your daughter.