Hello, Welcome to HCM, The bad odor from the mouth of your daughter following intake of some water paint, the intake of the paint into the mouth may have lead to infection of the oral cavity and the gastrointestinal tract. Infection of the oral mucosa can lead to bad breath of your daughter or the paint which she has consumed may have lead to gastric irritation and lead to symptoms of gastritis and leading to bad halistosis. I would suggest you to follow these remedies Clean her mouth repeatedly Syp Bactoclav Syp Mucaine gel These remedies will helps to reduce these symptoms and if the symptoms are not coming down even after the treatment you have to consult your pediatrician at the earliest. Thank you