What of fact W. Harrington says Our Lady did not believe in Him, as shown in Mk 3:20 ff.

But Mark would not contradict Luke, who shows her as first believer. If she went with that group - uncertain - she need not have agreed with them, might have wanted to hold them down, as most mothers would do. When did Our Lady learn Jesus was to be Messiah? Soon as Angel said He would reign over house of Jacob forever - then all the prophecies would begin to come to mind.