A lot of the main stream camping food will say if it is vegetarian or not right on the container. Also, those Kikkoman Miso soup packets are usually pretty good (though pricy.) Taste of India (found in many grocery stores) has what I call Indian MREs - they are a bit heavy, because they are hydrated - but I enjoy them. If you go to REI's website, and choose the food subsection, there are check-boxes on the left, one of which is vegetarian. That may be of some help. Unless s/he doesn't drink milk / eat eggs. I have camped with one vegan, and know several vegetarians - and each vegetarian has their own will and won'ts (eggs / milk / fish) - but I'm sure s/he has shared what level they are at with you.

HTH