Your contention is incorrect on several counts, McLees
. Of course the Apostles don't mention praying to Mary as the Blessed Mother was a contemporary and very much alive at the time of the events of the NT. I have no doubt they prayed with
her and asked for her prayers, and each others, as she is mentioned as being with them, "after the Gospels", (which you asked if she was), in Acts. In fact, Mary is the only one to be mentioned by name – other than the twelve Apostles and the candidates – of about 120 people gathered, after the Ascension, in the Upper Room on the occasion of the election of Matthias to the vacancy of Judas. The Early Church Fathers wrote extensively of her, although most all of their writings were primarily on doctrine and not written prayers, they all gave her the rightful place she still holds in the hearts of most Christians...http://www.staycatholic.com/ecf_immaculate_conception.htm
That is just some of the writings of the ECF's concerning the Immaculate Conception. One of the earliest surviving Marian prayers, that is still in use, is called the Ὑπὸ τὴν σὴν εὐσπλαγχνίαν, (Beneath your Compassion), which dates from the AD 200's, several generations before the reign of Constantine.
Beneath your compassion,
We take refuge, O Mother of God:
do not despise our petitions in time of trouble:
but rescue us from dangers,
only pure, only blessed one.
Ὑπὸ τὴν σὴν εὐσπλαγχνίαν,
Τὰς ἡμῶν ἱκεσίας,
μὴ παρίδῃς ἐν περιστάσει,
ἀλλ᾽ ἐκ κινδύνων λύτρωσαι ἡμᾶς,
μόνη Ἁγνή, μόνη εὐλογημένη.