Have you been through anything like this?
For more than 35 years.
I was prescribed Zantac in the early days of its existence. Back then it was prescription only, not yet an O.T.C. It made me more nauseous! (A side effect which is said to be rare).
There have been other prescriptions since then. Never had Omeprazole and other than occasionally taken TUMS or similar, nothing these days.
Similar to your daughter, it was and is not a daily occurrence.
My solution has been trying smaller portions spread through the day and early evening. Usually that works when it starts up. I also find cooler temps help ease any nausea.
Mine is also, they found, related to my esophagus. I have a peristaltic oddity. The test for that was rather unpleasant (tube with cold water running through and inserted through a nostril, down to and into the esophagus), it cleared my sinuses though.
As to a nutritionist, that's a good idea.