"They see the waitress."
Translation:Ei văd chelnerița.
Both "Ei văd chelnerița" and "Ei o văd pe chelneriță" are valid accusative forms which should be accepted here. The second form is more common when the grammatical object is a person, while the first form is more common when the grammatical object is an animal or a non-living thing. But there is some degree of overlap between them.