Do one numerology reading for each name, both with the real birth date. And see which applies most to the person your mother is today.

The numerology aspects of the name first recorded at birth is always with a person. When a name changes, its numerology aspects gradually become effective, combining with the original name's aspects.

After some years, the numerology aspects of the new name can become dominant. The aspects of the original name are still there. The new name's aspects are dominant because the new name has become more familiar and comfortable than the original name.

Because it has been so many years with the new name, my guess is the numerology reading for the new name will be more applicable to who your mother is today than will the numerology reading for the original name. Still, the numerology reading for the original name can be of use for its information. The original name's aspects are still with your mother, even if lacking dominance.

Should your mother change her name back to what it was originally, her characteristics should change more rapidly than they would changing to an entirely new name. The original name's aspects are still there. Changing her name back would empower those aspects.