I can't see any other way than to specifically research every ingredient that goes into what you give her. And hope for the best :-) Given the tomato thing I'd probably check how she is with other things from the same botanical family. Like egg-plant, for example.
Maybe also ask what she likes to eat and see where it intersects with what you are prepared to make.
In general most vegetables, fruits and beans are not allergens for the vast majority of the population. As I understand it the main problem allergens, the big 8, are milk, eggs, peanuts, tree nuts, fish, shellfish, soy and wheat.
| current weight: 146.0