Gastroesophageal Reflux Disease (GERD): The daily spitting up of small amounts without nausea, belly pain, or eating disorder suggests a chronic condition like GERD. The use of lactaid and wonderbelly calming pills indicates an attempt to manage symptoms that could be related to reflux.

Functional Dyspepsia: Given the absence of belly pain but the presence of daily spitting up, functional dyspepsia could be a consideration, especially if the spitting up is postprandial and related to eating.
Rumination Syndrome: This condition involves the repeated regurgitation of food, which can occur shortly after eating. The fact that she spits up daily, approximately 1-1.5 cups, could suggest rumination, especially if the content is food that has been recently eaten.
Lactose Intolerance: Although she takes lactaid, which suggests an awareness of lactose intolerance, incomplete digestion of lactose could still lead to gastrointestinal symptoms, including spitting up, if the lactaid is not fully effective or if lactose intake exceeds the capacity of the lactaid to digest it.

Eosinophilic Esophagitis: This is a condition characterized by inflammation of the esophagus due to an allergic reaction, which can cause difficulty swallowing, food impaction, and regurgitation. It's crucial to consider this diagnosis due to its potential for severe complications if left untreated.
Gastric Outlet Obstruction: Although less likely given the absence of nausea and vomiting, any condition causing a mechanical obstruction could lead to regurgitation of food. This would be a critical diagnosis to miss, as it requires urgent medical intervention.
Inflammatory Bowel Disease (IBD): Conditions like Crohn's disease or ulcerative colitis can have extraintestinal manifestations and could potentially cause gastrointestinal symptoms, including regurgitation, although this is less common.

Achalasia: A rare disorder of the esophagus that makes swallowing difficult, leading to regurgitation of food. It's less common in children but should be considered in the differential diagnosis due to its significant impact on quality of life and the need for specific treatment.
Gastroparesis: A condition where the stomach takes too long to empty its contents, which can lead to nausea, vomiting, and regurgitation. It's less likely given the absence of nausea and the specific pattern of spitting up, but it remains a possibility, especially if other diagnoses are ruled out.