In Catholicism, what is the significance of Mary being κεχαριτωμένη in Luke 1:28?

Luke 1:28: > Καὶ [And] εἰσελθὼν [having entered] πρὸς [to] αὐτὴν [her] εἶπεν [he said], Χαῖρε [Greetings], **κεχαριτωμένη [having been graced/highly favored]**, ὁ [the] Κύριος [Lord] μετὰ [with] σοῦ [you]. NIV: > The angel went to her [Mary] and said, ‘Greetings, you who are highly favored! The Lord is with you.’ While many people in the NT are considered to have "χάρις" [grace], Mary is the only person described as being "κεχαριτωμένη" [having been graced/highly favored]. Do Catholics attach any particular significance to this choice of words in Luke? I will accept answers from the writing of the church itself, and from Catholic apologists.