The name of this Holy Day (Immaculate Conception) has become misleading.
The conception is not of Anna because it was Mary who was conceived.
I've also seen it called the "Maternity of Anna" which is correct but rather changes the focus.
The "Conception by Anna" is partially correct; more accurate is "Conception by Anna and Joachim."
A better name for the commemoration would be "Conception of the Theotokos" as it better matches the scriptural readings.
I tend to think that "Immaculate Conception' has merit
(understanding that my eastern brothers and sisters have arguable grounds for disagreement)
because the "Most Pure One" also has the title of the "New Eve." As Eve was created (in a different way) without sin,
it is logical that the mother of mankind was also created without sin.
IMHO, it becomes difficult to explain the Holy Day when we have such difficulty with the accuracy of its name.
A holy feast to all,
Fr Deacon Paul