Compound subject
A compound subject is when there are two or more subjects in the sentence. "Ona" and "Ashley" are both nouns and they work as the subject of the sentence. When there is a compound subject, the individual subjects are joined by a coordinating conjunction (and, or, neither, nor) and sometimes a comma. In the sentence given, the subjects are joined with "and".
Other examples of a compound subject are: "Matias, Joaquin, and Alex are fans of soccer", "Neither you nor your sister will go out", "The cat or the dog will have to go, we can't have them both!"