Patient seen at ED Dept for right upper quadrant abdominal pain, vomiting and diarrhea a diagnosis of probable gastroenteritis is made

A Newbie Coder friend asked me this question and wanted a 2nd opinion

I told her in Outpatient Codng guidelines she need to code the symtoms due to there's not a actual dx and a dx of probable gastroenteritis is not allowed as a proper dx code as she need to code the highest levle of of specificity. So I told her to code the only symptoms of :

789.01,787.03, 787.91 . As the Probable Gastroenteritis is not coded under ioutpatient guidelines as it would be allowed under Inpatient coding Guidelines.

Thanks for all and any of your inputs.