Little girl, age 8, woke up throwing up & it looks like chocolate milk. she ate 2 oreos 4 hours ago. should i be concerned?

Yes, but...: Black (not dark brown) vomit can indicate old blood. But nausea and other viral illnesses will cause delayed emptying of the stomach (normal is about 4 hours) so i suspect it is residual of the partially digested oreos. There is a chemical test for blood if she vomits again - just collect a small amount in a clean jar and take to your pediatricians office.