My mom thinks her stomach pain is from eating tomatoes/tomato sauce... she has had quite severe stomach pain since dinner time... she doesn't want to go to hospital... is there enything I can give her to try and alleviate the pain?

You can try pepto bismol, gingerale, rolaids. If this stomach ache persists she should see her doctor, but if there's no vomiting, diarrhea, fever, and it's only been since dinner, it's likely just an upset stomach, or the start of the flu.