In the scripture the Mother or heavenly mother would be the Church. A proper church that is a part of the Church is nourishing her children, the newer members, who need help in growing, to become mature properly fitted members of the Body, the Body of Christ.
Mary the mother of the man of flesh, Jesus, would be a type or shadow of the Mother, which is the Church. She was a very good type, but still a type. The Reality is the perfected Church, perfected by the Holy Spirit working through the ministers given by God for that purpose.
Simply saying that the Church is the Mother may not be easy to understand although I do believe it. Perhaps God will help us all to understand it better and agree:
"And Naomi said unto her two daughters in law, Go, return each to her mother's house: the LORD deal kindly with you, as ye have dealt with the dead, and with me." Ruth 1:8
Which mother was Naomi speaking of? And then which Mother did Ruth choose?
"And Ruth said, Entreat me not to leave thee, or to return from following after thee: for whither thou goest, I will go; and where thou lodgest, I will lodge: thy people shall be my people, and thy God my God:" Ruth 1:16
Orpah went back to her natural mother, but Ruth, a gentile as we are (or have been) gentiles, chose a new and better Way, a better Mother [Naomi was also a better shadow of the true Mother Church than her own natural mother back in Moab].
And then...
"For it is written, that Abraham had two sons, the one by a bondmaid, the other by a freewoman.
But he who was of the bondwoman was born after the flesh; but he of the freewoman was by promise.
Which things are an allegory: for these are the two covenants; the one from the mount Sinai, which gendereth to bondage, which is Agar.
For this Agar is mount Sinai in Arabia, and answereth to Jerusalem which now is, and is in bondage with her children.
But Jerusalem which is above is free, which is the mother of us all." Gal 4:22-26
"So then, brethren, we are not children of the bondwoman, but of the free" Gal 4:31
"Jesus answered and said unto him, Verily, verily, I say unto thee, Except a man be born again, he cannot see the kingdom of God.
Nicodemus saith unto him, How can a man be born when he is old? can he enter the second time into his mother's womb, and be born?
Jesus answered, Verily, verily, I say unto thee, Except a man be born of water and of the Spirit, he cannot enter into the kingdom of God.
That which is born of the flesh is flesh; and that which is born of the Spirit is spirit." John 3:3-6
Who is the Mother giving birth as per John 3?
"And a certain man lame from his mother's womb was carried, whom they laid daily at the gate of the temple which is called Beautiful, to ask alms of them that entered into the temple;" Acts 3:2
"Then Peter said, Silver and gold have I none; but such as I have give I thee: In the name of Jesus Christ of Nazareth rise up and walk.
And he took him by the right hand, and lifted him up: and immediately his feet and ankle bones received strength.
And he leaping up stood, and walked, and entered with them into the temple, walking, and leaping, and praising God." Acts 3:6-8
What Mother gave new Life to that man who had been born lame to his natural mother?
So who or what is Jerusalem? One literal translation of the word Jerusalem: "set ye double peace". [That brings to my mind the double portion that Jacob gave to Joseph. But that's another and a perhaps deeper subject.]
"And I saw a new heaven and a new earth: for the first heaven and the first earth were passed away; and there was no more sea.
And I John saw the holy city, new Jerusalem, coming down from God out of heaven, prepared as a bride adorned for her husband." Rev 21:1-2
Consider that a mother has children. We know how Ruth (Bride) had children effectively for her dead husband the son of Naomi (Mother Church) via Boaz. We can make it complicated, but it doesn't have to be if we trust God to help us in it:
"There are threescore queens, and fourscore concubines, and virgins without number.
My dove, my undefiled is but one; she is the only one of her mother, she is the choice one of her that bare her. The daughters saw her, and blessed her; yea, the queens and the concubines, and they praised her." Song of Solomon 6:8-9
The only one of her Mother, the Church, is the Bride of Christ, born again among older brothers and sisters who as the Mother nourished each child until that child could become a member of the Bride.
"And he gave some, apostles; and some, prophets; and some, evangelists; and some, pastors and teachers;
For the perfecting of the saints, for the work of the ministry, for the edifying of the body of Christ:
Till we all come in the unity of the faith, and of the knowledge of the Son of God, unto a perfect man, unto the measure of the stature of the fulness of Christ:
That we henceforth be no more children, tossed to and fro, and carried about with every wind of doctrine, by the sleight of men, and cunning craftiness, whereby they lie in wait to deceive;
But speaking the truth in love, may grow up into him in all things, which is the head, even Christ:
From whom the whole body fitly joined together and compacted by that which every joint supplieth, according to the effectual working in the measure of every part, maketh increase of the body unto the edifying of itself in love." Eph 4:11-16
The Church is the spiritual Mother that took us in and nourished us properly with the flesh and blood of Jesus so that we could have the Life which he is... so that we could speak that words of the Father as Jesus did... so that we could walk the walk that Jesus walked along the "highway of holiness".