Lou Ann tells Adrienne that Malcolm is 110 years old. The photo of Malcolm and Carno reads "Carno and Malcolm, 1897". When Adrienne gives the photo to Malcolm, he says he was ten when it was taken. Since the game takes place in 1995, Malcolm would 108 years old, not 100.
If Adrienne examines the magic book any time before Don takes it, she just turns some pages and mentions that "it has been long since Latin class". However, during that altar room scene, it takes her very shortly to find the correct page with the spell she needs, and suddenly she become almost fluent in Latin.