Thanks for all your replies.
We were lying down in silence tonight and her stomach was growling even worse than mine, so I brought up the celiac issue. I told her if she doesn't treat it she may die younger than she otherwise should, and also suffer many health issues in the coming years. She just laughed and she's not going to die on me. She hasn't had any real issues from it yet, so I can understand why she's not too fussed. I can't dictate anything to anyone so I guess I'll just need to wait and see how this all pans out.