The following sentence comes from lines 74–75 of chapter XXV of Lingua latina per se illustrata. Familia Romana, after Ariadna has said some words to Theseus:
Haec locūta, Ariadna Thēseō fīlum longum dedit
This explanation is written in the margin of the book:
haec locūta = postquam haec locūta est
This clarifies the meaning of the expression haec locūta. In addition, since it says est, I see that haec locūta must be singular: it cannot be neuter plural. So it must be feminine singular, but I'm not able to understand why. Why is the feminine used here? In chapter XXI (lines 123–124), we find this other sentence
Mārcus ipse haec scripsit et ā magistrō laudātus est
with the margin note
haec (n pl) = hae rēs
So, why isn't neuter (plural or even singular, hōc locūtum) used in the first sentence?