Can somebody please tell me what the role of the Nurse is in Euripides' Medea?

In Euripides' Medea, which was first
staged in 431 BCE in Athens, the play opens with a lamentation by Medea's nurse, who
wishes that Jason and the Argonauts had never come to Colchis, Medea's native
land.

Oh how
I wish that ship the Argo
had never sailed off to the land of
Colchis,
past the Symplegades, those dark dancing rocks
which smash
boats sailing through the Hellespont.

(Ian Johnston
translation)

Medea's nurse is
an elderly servant who would have nursed Medea when Medea was a baby. It seems to have
been common in some ancient societies for a woman other than the child's mother to nurse
the child. In addition to nursing the infant child, the nurse would have remained with
the child's servant as long as the nurse and the child remained alive. Compare Homer's
Odyssey, where Odysseus' nurse is still alive and well in his
palace after many years.

In plays like Euripides'
Hippolytus, the nurse serves as a confidant for her mistress
Phaedra, eventually persuading her to confess her love for her stepson Hippolytus and
make an indecent proposal to the young man.

In
Medea, however, the title character serves to help provide
background for the play and explain Medea's current mood. Medea's nurse does not have a
speaking role in the last four-fifths of the play.