Welcome Ger42 to the Crohns Forum. I have heard from some other HW members that our Prostate Forum is quite good and understanding...I hope you find the same support here at the Crohns.
First of all let me say that you too have really delt with alot. Stress is the key reason Crohns does flare and if she's been worried about your health than the two of you have been in circles. It sounds to me also that she might be dealing with an obstruction. What leads me to think this is the "NO" BM when she's doing poorly and then vomiting... this can be a serious situation when that happens.... if that was me I would go to the E.R. right away!
I sincerely hope that she find a good G.I. to nail down what is actually happening. Finding an obstruction can be tricky... it took a CT scan with Barrium constrast to find mine. My Crohns does not show up in my blood tests either.
When I'm having rough times...I do a low-residue diet. You can Google this to find out what it means. It usually consist of things that are easily broke down and easy to digest. Also, I know of a few people here who are chatting thursday nights on the Crohns chat 6-9 p.m. she is always welcome and can ask questions there.
Best Wishes