The Greek word for 'mother' is meter and is used in such verses as Matthew 1:18 & 2:11 where Mary has the word 'mother' applied to her. It is also used in John 2:1: "...Jesus' mother was there..."
The Greek word for 'woman' is gune and is used by Jesus in John 2:4, so this does, indeed, give rise to the question as to why Jesus called her 'woman', and not 'mother'. When John wrote that chapter, he must have had reason to speak of Mary as Jesus' mother in verse 1, yet record Jesus calling her 'woman' in verse 4.
Some translations put verse 4 as "Dear woman..." (such as the N.I.V.) but the word for "dear" is not in the Greek text. An intriguing combination of Jesus using those two different words occurs at the crucifixion:
"When Jesus saw his mother there, and the disciple whom he loved
standing near by, he said to his mother, "Woman, here is your son,"
and to the disciple, "Here is your mother." John 19:26-27 N.I.V. 1987
ed.
When we consider the visionary woman of Revelation 12:1-6 who gave birth to a male child, with that prophetic book also speaking of the great marriage supper of the Lamb (the risen Christ), there is likely a spiritual aspect to all that was said and done at that marriage in Cana. Here is a snippet from a book that explores the signs Jesus performed as recorded in the gospel of John:
"This travail culminates in 'the mother of Jesus', who, preceding him
after the flesh, brought him forth as to his manhood. And if so, she
signifies all who travailed of the spiritual in Israel... And take
notice that up to John 2:1 no mention is made of how the logos was
made flesh. When eventually it is mentioned, the name 'Mary' is
conspicuous by its absence.
What is present, in a mystery, is the unusual expression, 'the mother
of Jesus'. Likewise that Jesus calls her 'Woman', verse 4. Unmentioned
before: unnamed now. Why? It is a sign... The mother of Jesus was
there; only when she spoke did he acknowledge her, and that merely as
'Woman'. And as if that were not enough, added, 'What have I to do
with thee?' What else could warrant such terminology, save the
Spirit's fashioning a sign?
With what was signified, then came 'Jesus and his disciples'. If she
figured the inclusion and culmination of all the travailing children
of God up to the coming of the promised Seed, surely 'Jesus and his
disciples' depicted - in such a vision - 'Christ and the ekklesia',
Ephesians 5:30-32. If so, at 'the marriage', alluding to the marriage
of the Lamb, there appears in a figure the general assembly and
ekklesia of the firstborn whose names are written in heaven...
To return to the thing signified - so far - to the sign itself, next
to be observed is that of which the mother of Jesus took notice, but,
apparently, he did not. But over this for the first time she addressed
him. Not with a question, neither a request. Just a bald statement.
'And when they wanted wine, the mother of Jesus saith unto him, They
have no wine,' verse 3.
So? What was he supposed to do? Why tell him? Because she was given
to have divine discernment, and with it, the Spirit of prophecy. She
perceived that God had created this providence. The more remarkable
the restraint and propriety of her utterance, knowing that the
circumstances were of God, the prelude on the third day of the first of
the signs to the work of power.
He discourages her. Rebuffs her: 'Jesus saith unto her, Woman, what
have I to do with thee? Mine hour is not yet come', verse 4.
No, it was not. But the figure of it was, and she knew it. The
spiritual penetration of her discernment left her in no doubt both
that this was God's overruling, and likewise of his certain
response.
Ignoring him, her faith equal to the trial, 'His mother saith unto the
servants, Whatsoever he saith unto you, do it,' verse 5. For her soul
and spirit within her sang with a mighty witness: he would, he must
respond: for this thing was of God." John chapters 1 to 12 The
First Six Signs, John Metcalfe, pp. 148-150, 2006,
http://www.johnmetcalfepublishingtrust.co.uk/contact_us.htm
Then follows 12 pages of detailed exposition of the meaning of the sign Jesus performed at Cana. But enough has been given here to show that the startling nature of the wording, Mary being called 'woman' by her Son, is meant to make us think more deeply about symbolic meanings under the surface of a wedding where Jesus' performed this, his first sign. It may appear rude to us, but its spiritual significance is not to be lost.