If her symptoms improved low-dose why did you stop treatment? My golden rule is to continue what works. Recommence therapy, and if you improves (and more importantly, continues to improve) then stay with treatment for some time. Discontinue when NO more benefit is derived form treatment. No rules here. It amazes me how some folks do a "course" of treatment, and then...stop!
The alternative is to have a comprehensive stool test performed on her, and to see if there are any underlying reasons for her nausea when she eats. If she is not improving on her current regime, then stop and go back to what did work, let me know the outcome.