The usage of “banzai”

Solution 1:

To expand on the "battle cry" usage, Wikipedia has the term Banzai charge.

A Banzai charge is the term used by the Allied forces to refer to Japanese human wave attacks mounted by infantry units. This term came from the Japanese cry "Tenno Heika Banzai" (天皇陛下萬歲?, "Long live the Emperor"), shortened to banzai, specifically referring to a tactic used by Japanese soldiers during the Pacific War. Banzai charges had some successes at the ends of battles by overcoming soldiers unprepared for such attacks.

A human wave attack is an attack where masses of people attack, hoping to overwhelm the opponent even if they suffer great casualties themselves.

Japanese soldiers in World War 2 had a reputation for being very fearless or reckless. The kamikaze attacks would be an example of this, but as another example, Australian Prime Minister John Curtin described the Cowra breakout of Japanese POWs as showing a "suicidal disregard of life".

As an example of "banzai" being used in everyday English, Garfield shouts "banzai!" whenever he launches an attack.

I assume that Mapp must have been very fearless or reckless in trying to what she was trying to do. Or to put it another way as suggested in the comments by Frank, Mapp must have had total comittment to the book.

Solution 2:

To refer to an earlier thread (Where does the phrase "balls to the wall" come from?), she went balls to the wall in her studying.