The Sicilian and Mama Corleone

I just finished the Sicilian the other day and was rather intigued by the passage describing Mike's homecomming. The book says that Mama Corleone embraces Mike and he is suprised by this because she'd only done this once before ( upon his return form the army). It stood out to me becuase I had never heard her described as unaffectionate in the book or other movies.. what do u guys think?

In that particular incident she's somewhat icy with him, but as you see in GF movies she's very open to listen to him and tell him how family cant be lost. I think it's just an isolated occurance, but I may be wrong.. havent read all the books