has no bearing on the discussion, and whether of not Jesus' Mother, Mary was alive in 90 AD is completely irrelevant as well.
The point was that St. John took Our Blessed Mother into his home at the foot of the cross, per Our Lord's direction:
John 19: 25-27
https://www.biblegateway.com/passage/?search=John+19&version=RSVCE
25 So the soldiers did this. But standing by the cross of Jesus were his mother, and his mother’s sister, Mary the wife of Clopas, and Mary Mag′dalene. 26 When Jesus saw his mother, and the disciple whom he loved standing near, he said to his mother, “Woman, behold, your son!” 27 Then he said to the disciple, “Behold, your mother!” And from that hour the disciple took her to his own home.[c]
Our Blessed Mother was alive and was well known by the Apostles and other disciples. She knew when Jesus was born, and so did they.
The earliest written records we have indicating when they celebrated His birthday:
St. Theophilus, Bishop of Caesarea died c. 181 AD. He was a bishop in Palestine where Jesus' Mother, Mary was. He wrote:
"We ought to celebrate the birth of Our Lord on what day soever the 15th of December shall happen."
St. Hippolytus of Rome died 235 AD
"The first advent of Our Lord in the flesh occurred when He was born in Bethlehem on December 25th."